Method and apparatus for plmn selection and cell (re)selection

ABSTRACT

A method and an apparatus for wireless communications are provided. The method is performed by a UE and includes: reading system information of a plurality of cells on a first carrier frequency to obtain identification information of a plurality of PLMNs; reporting, by an AS entity of the UE, the identification information of the plurality of PLMNs to a NAS entity of the UE; selecting, by the NAS of the UE, one of the plurality of PLMNs as a selected PLMN; searching for the plurality of cells on the first carrier frequency during a cell selection procedure; and selecting a suitable cell belonging to the selected PLMN from the plurality of cells on the first carrier frequency based on the cell selection procedure.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of U.S. patentapplication Ser. No. 16/728,961 filed on Dec. 27, 2019, which claims thebenefit of and priority to a provisional U.S. Patent Application Ser.No. 62/788,223, filed on Jan. 4, 2019, the contents of all which arehereby fully incorporated herein by reference for all purposes.

FIELD

The present disclosure generally relates to wireless communications, andmore particularly, to methods and apparatuses for Public Land MobileNetwork (PLMN) selection and cell (re)selection.

BACKGROUND

Various efforts have been made to improve different aspects of wirelesscommunications (e.g., data rate, latency, reliability, and mobility) forthe next-generation (e.g., fifth generation (5G) New Radio (NR))wireless communication systems. For example, to achieve higher capacityand promote higher spectrum utilization, the next-generation wirelesscommunication systems may be enabled to operate on unlicensed spectrums.However, the current Radio Resource Control (RRC)_IDLE or RRC_INACTIVEstate to RRC_CONNECTED state transition procedures, such as PLMNselection and cell (re)selection procedures, may not be adequate for UEsattempting to utilize the unlicensed spectrums to access the network inthe next-generation wireless communication systems.

Therefore, there is a need in the art for providing methods andapparatuses for performing PLMN selection and cell (re)selection on theunlicensed spectrum(s).

SUMMARY

The present disclosure is directed to methods and apparatuses for PLMNselection and cell (re)selection.

According to an aspect of the present disclosure, a User Equipment (UE)for wireless communications is provided. The UE includes one or morenon-transitory computer-readable media having computer-executableinstructions embodied thereon and at least one processor coupled to theone or more non-transitory computer-readable media. The at least oneprocessor is configured to execute the computer-executable instructionsto read system information of a plurality of cells on a first carrierfrequency to obtain identification information of a plurality of PublicLand Mobile Networks (PLMNs); report, by an Access Stratum (AS) entityof the UE, the identification information of the plurality of PLMNs to aNon-Access Stratum (NAS) entity of the UE; select, by the NAS of the UE,one of the plurality of PLMNs as a selected PLMN; search for theplurality of cells on the first carrier frequency during a cellselection procedure; and select a suitable cell belonging to theselected PLMN from the plurality of cells on the first carrier frequencybased on the cell selection procedure.

According to another aspect of the present disclosure, a methodperformed by a UE for wireless communications is provided. The methodincludes reading system information of a plurality of cells on a firstcarrier frequency to obtain identification information of a plurality ofPLMNs; reporting, by an AS entity of the UE, the identificationinformation of the plurality of PLMNs to a NAS entity of the UE;selecting, by the NAS of the UE, one of the plurality of PLMNs as aselected PLMN; searching for the plurality of cells on the first carrierfrequency during a cell selection procedure; and selecting a suitablecell belonging to the selected PLMN from the plurality of cells on thefirst carrier frequency based on the cell selection procedure.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. Variousfeatures are not drawn to scale. Dimensions of various features may bearbitrarily increased or reduced for clarity of discussion.

FIG. 1 illustrates a flowchart for a method of performing PLMN selectionand cell (re)selection procedures on an unlicensed spectrum, inaccordance with an example implementation of the present disclosure.

FIG. 2A is a schematic diagram illustrating a PLMN selection procedure,in accordance with an example implementation of the present disclosure.

FIG. 2B is a schematic diagram illustrating a cell selection procedure,in accordance with an example implementation of the present disclosure.

FIG. 3 illustrates a flowchart for a method of performing PLMN selectionand cell (re)selection procedures on an unlicensed spectrum, inaccordance with an example implementation of the present disclosure.

FIG. 4A illustrates a flowchart for a cell reselection procedure, inaccordance with an example implementation of the present disclosure.

FIG. 4B illustrates a flowchart for a cell reselection procedure, inaccordance with an example implementation of the present disclosure.

FIG. 5 illustrates a flowchart for a cell reselection procedureperformed when a UE cannot find a new suitable cell on a carrierfrequency, in accordance with an example implementation of the presentdisclosure.

FIG. 6 is a schematic diagram illustrating a cell reselection procedure,in accordance with an example implementation of the present disclosure.

FIG. 7 is a schematic diagram illustrating a message flow between the ASentity and the NAS entity of a UE, in accordance with an exampleimplementation of the present disclosure.

FIG. 8 is a block diagram illustrating a node for wirelesscommunication, in accordance with various aspects of the presentdisclosure.

DETAILED DESCRIPTION

The following description contains specific information pertaining toexample implementations in the present disclosure. The drawings in thepresent disclosure and their accompanying detailed description aredirected to merely example implementations. However, the presentdisclosure is not limited to merely these example implementations. Othervariations and implementations of the present disclosure will occur tothose skilled in the art. Unless noted otherwise, like or correspondingelements among the figures may be indicated by like or correspondingreference numerals. Moreover, the drawings and illustrations in thepresent disclosure are generally not to scale and are not intended tocorrespond to actual relative dimensions.

For the purpose of consistency and ease of understanding, like featuresmay be identified (although, in some examples, not shown) by the samenumerals in the example figures. However, the features in differentimplementations may be different in other respects, and thus shall notbe narrowly confined to what is shown in the figures.

The description uses the phrases “in one implementation,” or “in some ofthe present implementations,” which may each refer to one or more of thesame or different implementations. The term “coupled” is defined asconnected, whether directly or indirectly through interveningcomponents, and is not necessarily limited to physical connections. Theterm “comprising,” when utilized, means “including, but not necessarilylimited to”; it specifically indicates open-ended inclusion ormembership in the so-described combination, group, series and theequivalent. The expression “at least one of A, B and C” or “at least oneof the following: A, B and C” means “only A, or only B, or only C, orany combination of A, B and C.”

Additionally, for the purposes of explanation and non-limitation,specific details, such as functional entities, techniques, protocols,standard, and the like are set forth for providing an understanding ofthe described technology. In other examples, detailed description ofwell-known methods, technologies, systems, architectures, and the likeare omitted so as not to obscure the description with unnecessarydetails.

Persons skilled in the art will immediately recognize that any networkfunction(s) or algorithm(s) described in the present disclosure may beimplemented by hardware, software or a combination of software andhardware. Described functions may correspond to modules which may besoftware, hardware, firmware, or any combination thereof. The softwareimplementation may comprise computer-executable instructions stored oncomputer-readable medium such as memory or other type of storagedevices. For example, one or more microprocessors or general-purposecomputers with communication processing capability may be programmedwith corresponding executable instructions and carry out the describednetwork function(s) or algorithm(s). The microprocessors orgeneral-purpose computers may be formed of Applications SpecificIntegrated Circuitry (ASIC), programmable logic arrays, and/or using oneor more Digital Signal Processor (DSPs). Although some of the exampleimplementations described in this specification are oriented to softwareinstalled and executing on computer hardware, nevertheless, alternativeexample implementations implemented as firmware or as hardware orcombination of hardware and software are well within the scope of thepresent disclosure.

The computer-readable medium includes but is not limited to RandomAccess Memory (RAM), Read-Only Memory (ROM), Erasable ProgrammableRead-Only Memory (EPROM), Electrically Erasable Programmable Read-OnlyMemory (EEPROM), flash memory, Compact Disc Read-Only Memory (CD-ROM),magnetic cassettes, magnetic tape, magnetic disk storage, or any otherequivalent medium capable of storing computer-readable instructions.

A radio communication network architecture (e.g., a Long Term Evolution(LTE) system, an LTE-Advanced (LTE-A) system, an LTE-Advanced Prosystem, or a 5G NR Radio Access Network (RAN)) typically includes atleast one Base Station (BS), at least one UE, and one or more optionalnetwork elements that provide connection towards a network. The UEcommunicates with the network (e.g., a Core Network (CN), an EvolvedPacket Core (EPC) network, an Evolved Universal Terrestrial Radio AccessNetwork (E-UTRAN), a 5G Core (5GC), or an internet), through a RANestablished by one or more BSs.

It should be noted that, in the present application, a UE may include,but is not limited to, a mobile station, a mobile terminal or device, ora user communication radio terminal. For example, a UE may be a portableradio equipment, which includes, but is not limited to, a mobile phone,a tablet, a wearable device, a sensor, a vehicle, or a Personal DigitalAssistant (PDA) with wireless communication capability. The UE isconfigured to receive and transmit signals over an air interface to oneor more cells in a radio access network.

A BS may be configured to provide communication services according to atleast one of the following Radio Access Technologies (RATs): WorldwideInteroperability for Microwave Access (WiMAX), Global System for Mobilecommunications (GSM, often referred to as 2G), GSM Enhanced Data ratesfor GSM Evolution (EDGE) Radio Access Network (GERAN), General PacketRadio Service (GPRS), Universal Mobile Telecommunication System (UMTS,often referred to as 3G) based on basic Wideband-Code Division MultipleAccess (W-CDMA), High-Speed Packet Access (HSPA), LTE, LTE-A, eLTE(evolved LTE, e.g., LTE connected to 5GC), NR (often referred to as 5G),and/or LTE-A Pro. However, the scope of the present application shouldnot be limited to the above-mentioned protocols.

A BS may include, but is not limited to, a node B (NB) as in the UMTS,an evolved Node B (eNB) as in the LTE or LTE-A, a Radio NetworkController (RNC) as in the UMTS, a Base Station Controller (BSC) as inthe GSM/GERAN, a ng-eNB as in an Evolved Universal Terrestrial RadioAccess (E-UTRA) BS in connection with the 5GC, a next generation Node B(gNB) as in the 5G-RAN, and any other apparatus capable of controllingradio communication and managing radio resources within a cell. The BSmay serve one or more UEs through a radio interface.

The BS is operable to provide radio coverage to a specific geographicalarea using a plurality of cells forming the radio access network. The BSsupports the operations of the cells. Each cell is operable to provideservices to at least one UE within its radio coverage. Morespecifically, each cell (often referred to as a serving cell) providesservices to serve one or more UEs within its radio coverage (e.g., eachcell schedules the downlink and optionally uplink resources to at leastone UE within its radio coverage for downlink and optionally uplinkpacket transmissions). The BS can communicate with one or more UEs inthe radio communication system through the plurality of cells. A cellmay allocate Sidelink (SL) resources for supporting Proximity Service(ProSe) or Vehicle to Everything (V2X) service. Each cell may haveoverlapped coverage areas with other cells.

As discussed above, the frame structure for NR is to support flexibleconfigurations for accommodating various next-generation (e.g., 5G)communication requirements, such as Enhanced Mobile Broadband (eMBB),Massive Machine Type Communication (mMTC), Ultra-Reliable andLow-Latency Communication (URLLC), while fulfilling high reliability,high data rate and low latency requirements. The OrthogonalFrequency-Division Multiplexing (OFDM) technology as agreed in the3^(rd) Generation Partnership Project (3GPP) may serve as a baseline forNR waveform. The scalable OFDM numerology, such as the adaptivesub-carrier spacing, the channel bandwidth, and the Cyclic Prefix (CP)may also be used. Additionally, two coding schemes are considered forNR: (1) Low-Density Parity-Check (LDPC) code and (2) Polar Code. Thecoding scheme adaption may be configured based on the channel conditionsand/or the service applications.

Moreover, it is also considered that in a transmission time interval TXof a single NR frame, a Downlink (DL) transmission data, a guard period,and an Uplink (UL) transmission data should at least be included, wherethe respective portions of the DL transmission data, the guard period,the UL transmission data should also be configurable, for example, basedon the network dynamics of NR. In addition, SL resources may also beprovided in an NR frame to support ProSe services or V2X services.

In addition, the terms “system” and “network” herein may be usedinterchangeably. The term “and/or” herein is only an associationrelationship for describing associated objects, and represents thatthree relationships may exist. For example, A and/or B may indicatethat: A exists alone, A and B exist at the same time, or B exists alone.In addition, the character “/” herein generally represents that theformer and latter associated objects are in an “or” relationship.

On a licensed spectrum, a UE may perform a PLMN selection procedurebased on the signal strength of cells (e.g., the measured ReferenceSignal Received Power (RSRP) from cells). The cells on the licensedspectrum may broadcast the identification information (e.g., PLMNIdentities (IDs)) of the PLMNs and the UE's preconfigured PLMNs. On eachlicensed carrier frequency, the AS entity of the UE may report the PLMNIDs broadcast by the cell with the strongest signal strength, to the NASentity of the UE. Generally, cells operating on a common licensedcarrier frequency may belong to the same PLMN.

There may be multiple PLMNs operating on one carrier frequency. Forexample, one or more unlicensed RAT technologies (e.g., standalone NewRadio-Unlicensed (NR-U)) may be introduced, meaning that multiple PLMNsmay operate their own cells on the same unlicensed spectrum. Thus, thePLMN selection and cell (re)selection procedures on the unlicensedspectrum need to be provided, especially considering the uncertainty ofchannel load and channel sharing among multiple PLMNs. In anotherexample, one or more PLMNs may operate on the same carrier frequency ifRAN sharing scenarios are considered. PLMN(s) may be public PLMN(s)and/or private PLMN(s). Thus, the PLMN selection and cell (re)selectionprocedures when multiple PLMNs are operating on one carrier frequencyneed to be provided. In the RAN sharing scenarios, a RAN (or a cell) maybe shared and operated by multiple PLMNs.

In some of the implementations, the UE may camp on a non-best cell on acarrier frequency (e.g., an unlicensed carrier frequency) if the bestcell does not belong to a selected PLMN or a registered PLMN (orequivalent PLMN). The best cell may be the highest-ranked cell amongcells on the same carrier frequency. The cells on the carrier frequencymay be ranked by a received radio signal quality and/or other measuredmetric value(s). For example, the best cell (or highest-ranked cell) maybe the cell having the best received radio signal quality on the carrierfrequency, while the non-best cell (or the non-highest-ranked cell orlower-ranked cell) may be the cell other than the best cell on thecarrier frequency.

It should be noted that the terms such as “best cell,” “strongest cell,”and “highest-ranked cell” may be interchangeable in some of the presentimplementations. Similarly, the terms such as “non-best cell,”“non-strongest cell,” “lower-ranked cell” and “non-highest-ranked cell”may be interchangeable in some of the present implementations.

In some of the implementations, all cells on a licensed carrierfrequency may belong to the same (equivalent) PLMN. Thus, after the PLMNselection, the licensed carrier frequency may be indirectly selected.The UE may then prioritize the cells, and camp on the strongest cell onthe licensed carrier frequency. Unlike the licensed spectrum operations,one or more of the cells sharing the same unlicensed carrier frequencymay belong to different PLMNs. If the UE prioritizes the cells and campson the strongest cell on the unlicensed carrier frequency after the PLMNselection, the UE may waste time and consume extra power on searchingfor the suitable cell, when the strongest cell does not belong to aselected/registered/equivalent PLMN. In view of this, PLMN selection andcell (re)selection methods for unlicensed spectrum operations areprovided in at least some of the present implementations.

It should be noted that the PLMN selection and the cell (re)selectionmethods described herein may be also applied to the licensed spectrumoperations.

FIG. 1 illustrates a flowchart for a method of performing PLMN selectionand cell (re)selection procedures on an unlicensed spectrum, inaccordance with an example implementation of the present disclosure. Asshown in FIG. 1, the method includes actions 102, 104, 106, 108 and 110,where actions 102, 104 and 106 may be performed during a PLMN selectionprocedure, and actions 108 and 110 may be performed during a cellselection procedure.

In action 102, a UE may read system information of a plurality of cellson a first carrier frequency to obtain identification information of aplurality of PLMNs. In some of the present implementations, the firstcarrier frequency may be an unlicensed carrier frequency. The pluralityof cells may include the strongest cell and non-strongest cells. Eachcell may broadcast the identification information of a plurality ofPLMNs in the system information (e.g., System Information Block 1(SIB1)).

In action 104, the AS entity of the UE may report the identificationinformation of the plurality of PLMNs to the NAS entity of the UE. ThePLMNs identified by the identification information of the plurality ofPLMNs reported by the AS entity of the UE to the NAS entity of the UEmay refer to the found PLMNs of the UE. The NAS entity of the UE may beused to provide the upper layer signaling (e.g., NAS signaling) betweenthe UE and the core network, and the AS entity of the UE may be used toprovide the lower layer signaling (e.g., RRC signaling) between the RANand the UE. For example, the AS entity may be used for transporting dataover the wireless connection and managing the radio resources. The ASentity may include, for example, one or more layers of a protocol stackincluding a physical (PHY) layer, a Medium Access Control (MAC) layer, aRadio Link Control (RLC) layer, a Packet Data Convergence Protocol(PDCP) layer, a Service Data Adaptation Protocol (SDAP) layer and an RRClayer. Each of the AS entity and the NAS entity of the UE may beimplemented using electronic hardware, computer software, or anycombination thereof.

In action 106, the NAS entity of the UE may select one of the pluralityof PLMNs as a selected PLMN. For example, the NAS entity of the UE maymaintain or store a list of registered/equivalent/subscribed PLMNs andselect the PLMN which is mapped to the list as the outcome (e.g., theselected PLMN) of the PLMN selection procedure.

In action 108, the UE may search for the plurality of cells on the firstcarrier frequency during a cell selection procedure. The UE may not onlysearch for the strongest cell but also search for additional cells onthe first carrier frequency during the cell selection procedure. In someimplementations, the additional cells may or may not have a signalstrength (e.g., RSRP, Reference Signal Received Quality (RSRQ)) above athreshold (e.g., the additional cells may fulfill the S criterion). Theplurality of cells may be searched based on certain (pre)configured orpredefined rules. For example, the plurality of cells may be theN-strongest (e.g., top N) cells on the first carrier frequency, where Nis a positive integer. In some of the present implementations, the valueof N may be predefined (e.g., defined by 3GPP specifications),preconfigured to the UE (e.g., stored in a Universal Subscriber IdentityModule (USIM) and/or stored in a Universal Integrated Circuit Card(UICC)), configured by cell(s) (e.g., via system information and/or viadedicated signaling), or determined based on UE implementation.

In action 110, the UE may select a suitable cell belonging to theselected PLMN from the plurality of cells on the first carrier frequencyas an outcome of the cell selection procedure. The suitable cell may ormay not be the strongest cell on the first carrier frequency.

FIG. 2A is a schematic diagram illustrating a PLMN selection procedure,in accordance with an example implementation of the present disclosure.FIG. 2B is a schematic diagram illustrating a cell selection procedure,in accordance with an example implementation of the present disclosure.

In FIG. 2A, there are K cells C1, C2, C3, . . . , and CK on carrierfrequency f1. In the example implementation as illustrated in FIGS. 2Aand 2B, carrier frequency f1 may be an unlicensed carrier frequency.However, this is only for illustrative purposes, and not intended tolimit the scope of the present disclosure. In some otherimplementations, carrier frequency f1 may be a licensed carrierfrequency.

Each cell on carrier frequency f1 may broadcast the identificationinformation of its corresponding PLMN(s) in the system information(e.g., SIB1). For example, cell C1 may broadcast PLMN ID #1 of PLMN #1to which cell C1 belongs; cell C2 may broadcast PLMN ID #2 of PLMN #2 towhich cell C2 belongs; cell C3 may broadcast PLMN ID #3 of PLMN #3 towhich cell C3 belongs; and cell CK may broadcast PLMN ID #2 of PLMN #2to which cell CK belongs. If a cell belongs to more than one PLMN, thecell may broadcast the corresponding PLMN identification information inthe system information (e.g., SIB1).

In the example implementation, cells C1 through CK may be ranked by a UEbased on a received radio signal quality (e.g., RSRP and/or RSRQ), forexample, from the strongest to the weakest. The UE may read the systeminformation of the N1-strongest cells on carrier frequency f1. The UEmay obtain the identification information of PLMNs from the systeminformation broadcast by these cells (e.g., N1-strongest cells). In someof the present implementations, the value of N1 may be predefined (e.g.,defined by 3GPP specifications), preconfigured to the UE (e.g., storedin a USIM and/or stored in a UICC), configured by cell(s) (e.g., viasystem information and/or via dedicated signaling), or determined basedon UE implementation. For example, if N1=3, the N1-strongest cells mayinclude cells C1, C2 and C3, where cell C1 may be the highest-rankedcell on carrier frequency f1, then cell C2 (the next (e.g., second)highest-ranked cell), and then cell C3 (the next highest-ranked cellafter cell C2, or the third highest-ranked cell). The UE may obtain theidentification information (e.g., including PLMN ID #1, PLMN ID #2 andPLMN ID #3) of PLMNs from cells C1, C2 and C3 in the broadcast systeminformation of cells C1, C2 and C3. The AS entity of the UE may report alist of available/found PLMNs (e.g., including PLMN ID #1, PLMN ID #2and PLMN ID #3) to the NAS entity of the UE for PLMN selection. The NASentity of the UE may then select one of the reported available/foundPLMNs as the outcome of the PLMN selection procedure. For example, PLMN#2 may be selected because it is mapped to one PLMN in the listmaintained or stored by the UE. In one implementation, the UE may readthe system information of the N4-strongest cells on carrier frequencyf1, wherein the signal strength of N4-strongest cells may be above athreshold (e.g., fulfill the S criterion). The UE may obtain theidentification information of PLMNs from the system informationbroadcast by these cells (e.g., N4-strongest cells). In some of thepresent implementations, the value of N4 may be predefined (e.g.,defined by 3GPP specifications), preconfigured to the UE (e.g., storedin a USIM and/or stored in a UICC), configured by cell(s) (e.g., viasystem information and/or via dedicated signaling), or determined basedon UE implementation. In one implementation, if the UE may findN0-strongest cells, where N0 is less than N1 in the N1-strongest cellcase or N0 is less than N4 in the N4-strongest cell case, the UE mayobtain the identification information of PLMNs from the systeminformation broadcast by these cells (e.g., N0-strongest cells). The ASentity of the UE may report the list of available/found PLMNs (e.g.,including the obtained identification information of PLMNs) to the NASentity of the UE for PLMN selection. The NAS entity of the UE may thenselect one of the reported available/found PLMNs as the outcome of thePLMN selection. In some of the present implementations, if the UE cannotselect a PLMN, or if the UE cannot select a suitable cell, when the UEperforms the PLMN selection or cell (re)selection based on the N0 or N1configuration on a carrier frequency, the UE may deprioritize thiscarrier frequency.

Once the PLMN is selected, the UE may perform the cell selectionprocedure to search for a suitable cell to camp on. For example, the UEmay search for the N2-strongest cells on carrier frequency f1, where N2is a positive integer. In some of the present implementations, the valueof N2 may be predefined (e.g., defined by 3GPP specifications),preconfigured to the UE (e.g., stored in a USIM and/or stored in aUICC), configured by cell(s) (e.g., via system information and/or viadedicated signaling), or determined based on UE implementation. As shownin FIG. 2B, if N2=3, the N2-strongest cells may include cells C1, C2 andC3. Cell C1 may be the highest-ranked cell on carrier frequency f1, thencell C2 (the next (e.g., second) highest-ranked cell), and then cell C3(the next highest-ranked cell after cell C2, or the third highest-rankedcell).

As described above, each of cells C1, C2 and C3 may broadcast theidentification information of its corresponding PLMN(s) in the systeminformation (e.g., SIB1). Based on the system information, the UE mayknow that cells C1, C2 and C3 belong to PLMN #1, PLMN #2 and PLMN #3,respectively, which means the N2-strongest cells on carrier frequency f1belong to different PLMNs. The UE may determine whether the suitablecell can be found in the N2-strongest cells (e.g., cells C1, C2 and C3)on carrier frequency f1, by checking whether these cells belong to theselected PLMN or a PLMN that is indicated as being equivalent to aregistered PLMN of the UE. As illustrated in FIG. 2B, cell C2 may beselected as the suitable cell for the UE to camp on because cell C2 hasthe strongest/best received radio signal quality (e.g., RSRP and/orRSRQ) among all cells (e.g., cells C2 and CK) belonging to the selectedPLMN (e.g., PLMN #2) on carrier frequency f1. In one implementation,cell C2 may be selected as the suitable cell for the UE to camp onbecause cell C2 is the highest-ranked cell among cells (e.g., cells C2and CK) belonging to the selected PLMN (e.g., PLMN #2).

It should be noted that even though the values of N1 and N2 are the samein the example implementation, in some of the present implementations,the values of N1 and N2 may be independently (pre)configured. In someother implementations, the value of N2 may depend on that of N1. N2 mayor may not have the same value as N1.

In some of the present implementations, the value(s) of one or more ofN1, N2, N0, and N4 may be independently (pre)configured. In some otherimplementations, the value of one of N1, N2, N0, and N4 may depend onthe value of another one of N1, N2, N0, and N4.

FIG. 3 illustrates a flowchart for a method of performing PLMN selectionand cell (re)selection procedures on an unlicensed spectrum, inaccordance with an example implementation of the present disclosure. Asshown in FIG. 3, the method includes actions 302, 304, 306 and 308.

In action 302, a UE may perform a PLMN selection procedure to select aPLMN.

In action 304, the UE may perform a cell selection procedure to select asuitable cell to camp on. The suitable cell may belong to the selectedPLMN.

In action 306, the UE may determine whether the selected suitable cellmeets a cell reselection criterion (e.g., the R criterion). The cellreselection criterion may be related to a change in the measured metricvalue (e.g., the S criterion) of the suitable cell. For example, oncethe signal quality of the selected suitable cell is getting worse anddeteriorates below a predetermined threshold, the cell reselectioncriterion may be fulfilled and trigger the UE to perform a cellreselection procedure to find a new suitable cell, as illustrated inaction 308. Conversely, in action 306, if the selected suitable celldoes not meet the cell reselection criterion, the UE may keep detectingwhether the current suitable cell meets the cell reselection criterion,as illustrated in FIG. 3. It should be noted that when the UE reselectsthe new suitable cell in action 308, the method may proceed back toaction 306, where the UE may continue to determine whether thereselected suitable cell meets a cell reselection criterion (e.g., the Rcriterion).

In one implementation, when the UE camps on a cell (e.g., a selectedsuitable cell during cell (re)selection procedures), the UE mayregularly search for a better cell according to the cell reselectioncriteria. If the UE finds a better cell, the UE may select a better cellas the suitable cell to camp on. In one implementation, the UE mayreselect a new suitable cell if at least one of the two conditions aremet: (1) the new suitable cell is better than the current serving/campedcell according to the cell reselection criteria during a time interval,and (2) more than 1 second has elapsed since the UE began camping on thecurrent serving/camped cell.

FIG. 4A illustrates a flowchart for a cell reselection procedure, inaccordance with an example implementation of the present disclosure.

In action 402, a UE may determine whether the highest-ranked cell on afirst carrier frequency belongs to the selected PLMN or the registeredPLMN (or the equivalent PLMN) of the UE.

If the outcome of action 402 is Yes, the UE may select thehighest-ranked cell as the new suitable cell in action 404. In thiscase, the UE may switch from the original suitable cell to the newsuitable cell to camp on. Conversely, if the outcome of action 402 isNo, the UE may prohibit the highest-ranked cell from being selected asthe new suitable cell for a period of time Ta in action 406. The lengthof Ta may be preconfigured in the UE or configured by the cell(s) (e.g.,via system information and/or via dedicated signaling). In oneimplementation, the maximum value of Ta may be 300 seconds.

In action 408, when the highest-ranked cell is not selected as thesuitable cell by the UE to camp on, the UE may further determine whetherthe next highest-ranked (e.g., the second highest-ranked) cell on thefirst carrier frequency belongs to the selected PLMN or the registeredPLMN (or equivalent PLMN) of the UE.

As described above, cells on a carrier frequency may be ranked by theircorresponding measured metric values. For example, the highest-rankedcell and the next highest-ranked cell on the first carrier frequency maybe ranked by a received radio signal quality (e.g., RSRP, RSRQ). In sucha case, the next highest-ranked cell may have a poorer received radiosignal quality than the highest-ranked cell.

In action 410, the UE may select the next highest-ranked cell as the newsuitable cell, when it is determined in action 408 that the nexthighest-ranked cell belongs to the selected PLMN or the registered PLMN(or equivalent PLMN) of the UE. In this case, the new suitable cell(belonging to the selected PLMN or a PLMN that is indicated as beingequivalent to a registered PLMN of the UE) may be a non-highest-ranked(e.g., a lower-ranked) cell among all cells on the first carrierfrequency.

In action 412, the UE may determine that the next highest-ranked cell isa non-suitable cell when the next highest-ranked cell does not belong tothe selected PLMN or the registered PLMN (or equivalent PLMN) of the UEas determined in action 408. In one implementation, the UE may prohibitthe next highest-ranked cell from being selected as the new suitablecell for a period of time Tb when the next highest-ranked cell isdetermined as a non-suitable cell. The length of Tb may be preconfiguredin the UE (e.g., stored in a USIM and/or stored in a UICC) or configuredby the cell(s) (e.g., via system information and/or via dedicatedsignaling). In one implementation, the maximum value of Tb may be 300seconds.

In action 414, the UE may determine whether the total number ofnon-suitable cells on the first carrier frequency reaches a specificnumber. In the example implementation, the value of the specific numbermay a positive integer. In some of the present implementations, thespecific number may be predefined (e.g., defined by 3GPPspecifications), preconfigured to the UE (e.g., stored in a USIM and/orstored in a UICC), configured by cell(s) (e.g., via system informationand/or via dedicated signaling) or determined based on UEimplementation.

If the outcome of action 414 is Yes, the procedure may go to node A,which continues to node A′ in FIG. 5. If the outcome of action 414 isNo, the procedure may go back to action 408, in which the UE maydetermine whether the next highest-ranked cell belongs to the selectedPLMN or the registered PLMN (or equivalent PLMN) of the UE. In oneimplementation, the term “the next highest-ranked cell” may refer to acell with the rank after the rank of the cell just being checked not tobe selected.

In the example implementation, when the highest-ranked cell is notselected as the suitable cell, the UE may iteratively perform a processon the first carrier frequency, until the new suitable cell is found onthe first carrier frequency or a specific number of cells on the firstcarrier frequency are determined as non-suitable. As illustrated in FIG.4, actions 408, 412 and 414 may be iteratively performed multiple timesif the UE is continuously unable to find a new suitable cell on thefirst carrier frequency.

FIG. 4B illustrates a flowchart for a cell reselection procedure, inaccordance with another example implementation of the presentdisclosure.

In action 420, a UE may determine whether the highest-ranked cell amongall non-prohibited cells on a first carrier frequency belongs to theselected PLMN or the registered PLMN (or the equivalent PLMN) of the UE.The non-prohibited cells may be the cells that are not currentlyprohibited from being selected as the new suitable cell for the UE tocamp on. The prohibited cells may be the cells that are currentlyprohibited from being selected (e.g., via a cell-specific timer) as thenew suitable cell for the UE to camp on.

If the outcome of action 420 is Yes, the UE may select thehighest-ranked cell as the new suitable cell in action 422. In thiscase, the UE may switch from the original suitable cell to the newsuitable cell to camp on. Conversely, if the outcome of action 420 isNo, the UE may prohibit the highest-ranked cell from being selected asthe new suitable cell for a period of time (e.g., Ta) in action 424. Thelength of Ta may be preconfigured in the UE (e.g., stored in a USIMand/or stored in a UICC) or configured by the cell(s) (e.g., via systeminformation and/or via dedicated signaling). In one implementation, themaximum value of Ta may be 300 seconds.

In action 426, the UE may determine that the highest-ranked cell is anon-suitable cell because the highest-ranked cell does not belong to theselected PLMN or the registered PLMN (or equivalent PLMN) of the UE.

In action 428, the UE may determine whether the total number ofnon-suitable cells on the first carrier frequency reaches a specificnumber. In the example implementation, the value of the specific numbermay be a positive integer. In some of the present implementations, thespecific number may be predefined (e.g., defined by 3GPPspecifications), preconfigured to the UE (e.g., stored in a USIM and/orstored in a UICC), configured by cell(s) (e.g., via system informationand/or via dedicated signaling) or determined based on UEimplementation.

If the outcome of action 428 is Yes, the procedure may go to node A,which continues to node A′ in FIG. 5. If the outcome of action 428 isNo, the procedure may go back to action 420.

In some of the present implementations, action 428 may be omitted. Insuch cases, once the highest-ranked cell is determined as a non-suitablecell in action 426, the procedure may directly proceed to node A. Insome other implementations, actions 424, 426 and 428 may be omitted. Insuch cases, once the outcome of action 420 is No, the procedure maydirectly proceed to node A.

FIG. 5 illustrates a flowchart for a cell reselection procedureperformed when a UE cannot find a new suitable cell on the first carrierfrequency, in accordance with an example implementation of the presentdisclosure. It should be noted that although actions 502 and 504 aredelineated as separate actions represented as independent blocks in FIG.5, these separately delineated actions should not be construed asnecessarily order dependent. The order in which the actions areperformed in FIG. 5 is not intended to be construed as a limitation, andany number of the described blocks may be combined in any order toimplement the method, or an alternate method. Moreover, at least one ofactions 502 and 504 may be omitted during the cell reselection procedurein some of the present implementations.

In the example implementation, when the UE finds that the total numberof non-suitable cells on the first carrier frequency reaches thespecific number, the cell reselection procedure may continue to node A′of FIG. 5. Then in action 502, the UE may deprioritize the first carrierfrequency in a set of carrier frequencies for the cell reselectionprocedure for a period of time (e.g., Tc). For example, the UE maysearch for the new suitable cell on different carrier frequencies duringthe cell reselection procedure, where each carrier frequency may beassigned with a corresponding reselection priority. Once the firstcarrier frequency is deprioritized (e.g., the reselection priority ofthe first carrier frequency is reduced), the UE may select anothercarrier frequency with a higher reselection priority than the firstcarrier frequency, in order to search for the new suitable cell on theselected carrier frequency during the later cell reselection procedure.In one implementation, once the UE deprioritizes the first carrierfrequency in a set of carrier frequencies for the cell reselectionprocedure, the UE may consider the first carrier frequency to have thelowest priority among the set of carrier frequencies. In some of thepresent implementations, the length of Tc may be preconfigured in the UEor configured by the cell(s) (e.g., via system information and/or viadedicated signaling). Tc may or may not have the same value as Ta.

In action 504, the UE may search for the new suitable cell on a secondcarrier frequency. In some of the present implementations, the secondcarrier frequency may be an unlicensed carrier frequency. In some otherimplementations, the second carrier frequency may be a licensed carrierfrequency. In one implementation, after the UE deprioritizes the firstcarrier frequency, the second carrier frequency may have the highestpriority among the set of carrier frequencies for cell reselectionprocedure.

FIG. 6 is a schematic diagram illustrating a cell reselection procedure,in accordance with an example implementation of the present disclosure.As illustrated in FIG. 6, cells C5, C3 and C1 on carrier frequency f1may be ranked by the received radio signal quality (e.g., RSRP and/orRSRQ), from the strongest to the weakest. Thus, cell C5 may be thehighest-ranked cell on carrier frequency f1, then cell C3, and then cellC1. It should be noted that because the channel/network conditions maychange over time, the ranking of cells on carrier frequency f1 may bedifferent as compared with FIGS. 2A and 2B.

In the example implementation, cells C5, C3 and C1 may broadcast theidentification information (e.g., PLMN ID #5, PLMN ID #3 and PLMN ID #1)of their corresponding PLMNs in the system information (e.g., SIB1).Based on the system information, the UE may know that cells C5, C3 andC1 belong to PLMN #5, PLMN #3 and PLMN #1, respectively. If theselected/registered/equivalent PLMN is PLMN #2, the UE may determinethat cell C5 (the highest-ranked cell on carrier frequency f1) isnon-suitable because cell C5 does not belong to PLMN #2. Based on thesame reason, the UE may also determine that cells C3 and C1 arenon-suitable cells. Because the UE cannot find the new suitable cellfrom the N3-strongest cells (if N3=3) on carrier frequency f1, the UEmay then search for the new suitable cell on another carrier frequencyf2, which may be a licensed carrier frequency or an unlicensed carrierfrequency.

On carrier frequency f2, the UE may follow the methods illustrated inFIGS. 4 and 5 to continue the cell reselection procedure. For example,the UE may determine whether the highest-ranked cell on carrierfrequency f2 belongs to the selected PLMN or the PLMN that is indicatedas being equivalent to the registered PLMN of the UE. If the outcome ofthe determination is Yes, the UE may select the highest-ranked cell oncarrier frequency f2 as the new suitable cell. Conversely, if theoutcome of the determination is No, the UE may prohibit thehighest-ranked cell on carrier frequency f2 from being selected as thenew suitable cell for a period of time (Td). In some of the presentimplementations, Td and Ta may be independently (pre)configured, so thelength of Td may be independent of the length of Ta. In some otherimplementations, the length of Td may depend on the length of Ta. Td mayor may not have the same length as Ta. In one implementation, themaximum value of Td may be 300 seconds.

In some of the present implementations, when the highest-ranked cell oncarrier frequency f2 is not selected as the new suitable cell, the UEmay iteratively perform a process on carrier frequency f2 until the newsuitable cell is found from the N3′-strongest cells on carrier frequencyf2 or the total number of non-suitable cells on carrier frequency f2reaches N3′, where N3′ is a positive integer. In some of the presentimplementations, the value of N3′ may be predefined (e.g., defined by3GPP specifications), preconfigured to the UE (e.g., stored in a USIMand/or stored in a UICC), configured by cell(s) (e.g., via systeminformation and/or via dedicated signaling), or determined based on UEimplementation. In some of the present implementations, the value of N3′may be independent of the value of N3. In some other implementations,the value of N3′ may depend on the value of N3. N3′ may or may not havethe same value as N3. In one implementation, the UE may not read thesystem information from all of the N3′-strongest cells before the UEfinds and camps on the new suitable cell on carrier frequency f2. Oncethe UE finds and camps on the new suitable cell on carrier frequency f2,the UE may not further read the system information from the nexthighest-ranked cell with the rank after that of the new suitable cell.Once the UE finds and camps on the new suitable cell on carrierfrequency f2, the UE may not further measure the received radio signalquality of the remaining cells on carrier frequency f2 for this cellreselection procedure. Once the UE finds and camps on the new suitablecell on carrier frequency f2, the UE may not further rank the remainingcells on carrier frequency f2 for this cell reselection procedure.

As illustrated FIG. 6, if N3′=3, the N3′-strongest cells may includecells C4, C6 and C2, where cell C4 may be the highest-ranked cell oncarrier frequency f2, then cell C6, and then cell C2. Cells C4, C6 andC2 may broadcast the identification information (e.g., PLMN ID #4, PLMNID #6 and PLMN ID #2) of their corresponding PLMNs in the systeminformation (e.g., SIB1). Based on the system information, the UE mayknow that cells C4, C6 and C2 belong to PLMN #4, PLMN #6 and PLMN #2,respectively, and (re)select cell C2 as a new suitable cell because cellC2 belongs to the selected PLMN #2.

FIG. 7 is a schematic diagram illustrating a message flow between the ASentity of the UE and the NAS entity of a UE, in accordance with anexample implementation of the present disclosure.

As illustrated in FIG. 7, the NAS entity 73 of the UE may provide amessage to the AS entity 71 of the UE in action 702. The message mayindicate which of one or more PLMN types are supported by the UE. Basedon the message, the AS entity 71 may or may not modify the list ofavailable PLMNs to be reported to the NAS entity 73. For example, the ASentity 71 may filter out some PLMNs, with PLMN types not supported bythe UE, from the list of PLMNs to be reported to the NAS entity 73. Insome of the present implementations, the one or more PLMN types mayinclude a public PLMN type, a private PLMN type, and a public andprivate PLMN type. In one implementation, if the NAS entity 73 of the UEdoes not provide a message to the AS entity 71 of the UE, it means thatthe UE supports (or needs) to select a public PLMN as the outcome ofPLMN selection. In one implementation, if the NAS entity 73 of the UEprovides a message to the AS entity 71 of the UE, and if the messageincludes a first indicator corresponding to the private PLMN type, itmeans that the UE supports (or needs) a private PLMN as the outcome ofPLMN selection. In one implementation, if the NAS entity 73 of the UEprovides a message to the AS entity 71 of the UE, and if the messageincludes a second indicator corresponding to the public and private PLMNtypes, it means that the UE supports (or needs) a public or private PLMNas the outcome of PLMN selection.

As mentioned above, multiple networks (e.g., PLMNs) may operate onunlicensed or licensed spectrums. In addition, multiple networks (e.g.,PLMNs) may share the same unlicensed carrier or the same licensedcarrier. Each network may be public, private or both. Public networks(e.g., public PLMNs) may (but not limited to) be provided by operatorsor virtual operators, which may provide radio services to the publicsubscribers. The public networks may own one or more licensed spectrumsand support the radio access technology on the licensed spectrum(s) aswell. The public networks may support the radio access technology onunlicensed spectrums as well. On the other hand, private networks (e.g.,private PLMNs) may (but not limited to) be provided by micro-operators,factories, or enterprises, which may provide radio services to theirprivate users (e.g., employees or machines). The private networks maysupport the radio access technology on the unlicensed spectrum(s). Ifthe private PLMNs own a licensed spectrum, the corresponding privatenetworks may support the radio access technology on the licensedspectrum as well.

It should be noted that even though the term “public PLMN” may be usedin some of the present implementations, such a term may be replaced byanother term “public network” because the techniques described thereinare not intended to be limited to the public PLMN(s) and may beapplicable to other types of public network(s). Similarly, even thoughthe term “private PLMN” may be used in some of the presentimplementations, such a term may be replaced by another term such as“private network” or “non-public network” (NPN) because the techniquesdescribed therein are not intended to be limited to the private PLMN(s)and may be applicable to other types of private/non-public network(s).In one implementation, the private network scenario may be a Stand-aloneNon-Public Network (SNPN), i.e., operated by an NPN operator and notrelying on network functions provided by a (public) PLMN. In anotherimplementation, the NPN scenario may be a Public Network Integrated NPN(PNI-NPN), i.e., a non-public network deployed with the support of a(public) PLMN. The SNPN(s) may be identified by PLMN ID and/or NetworkID (NID) broadcast in SIB1 of a cell supporting SNPN. The PNI-NPN may beidentified by PLMN ID and/or Cell Access Group (CAG) ID broadcast inSIB1 of a cell supporting PNI-NPN. The identification information of anSNPN (e.g., an SNPN ID) may include a PLMN ID and/or an NID. Theidentification information of a PNI-NPN (e.g., a PNI-NPN ID) may includea PLMN ID and/or a CAG ID. Each of the PLMN ID, the SNPN ID, and thePNI-NPN ID may be referred to as a PLMN-related ID. In some of thepresent implementations, the PLMN-related ID may be included in theidentification information of a PLMN.

In some of the present implementations, public PLMNs and private PLMNsmay support several deployment scenarios. For example, the deploymentscenarios may include the carrier aggregation between the licensed band(e.g., NR, for the Primary Cell (PCell)) and the unlicensed band (e.g.,NR-U, for the Secondary Cell (SCell)), wherein the unlicensed SCell mayhave both DL and UL, or DL-only; the dual connectivity (ormulti-connectivity) between the radio access technology on the licensedband (e.g., LTE, NR, for the PCell) and the radio access technology onthe unlicensed band (e.g., NR-U, for the Primary Secondary Cell(PSCell)); the dual connectivity (or multi-connectivity) between thelicensed band (e.g., LTE, for the PCell) and the stand-alone radioaccess technology (e.g., stand-alone NR-U) on the unlicensed band; an NRcell with DL in unlicensed band and UL in licensed band; and thestand-alone unlicensed radio access technology (e.g., stand-alone NR-U).In some of the present implementations, private PLMNs may mainly support(but not limited to) the stand-alone unlicensed radio access technology(e.g., stand-alone NR-U).

During the PLMN selection procedure, the AS entity of the UE may reportavailable PLMNs to the NAS entity of the UE on request from the NASentity of the UE or automatically in some of the presentimplementations. In some of the present implementations, the NAS entityof the UE may inform the AS entity of the UE of which PLMN type (e.g.,public, private, both) the UE supports (as illustrated in FIG. 7).

In some of the present implementations, the AS entity of the UE may bepreconfigured with the information of which PLMN type (e.g., public,private, both) the UE supports. In some of the present implementations,if the UE supports pubic PLMNs only, the AS entity of the UE may reportthe available public PLMNs to the NAS entity of the UE. In some of thepresent implementations, if the UE supports the private PLMNs only, theAS entity of the UE may report the available private PLMNs to the NASentity of the UE. In some of the present implementations, if the UEsupports pubic PLMNs and private PLMNs, the AS entity of the UE mayreport the available public PLMNs and/or private PLMNs to the NAS entityof the UE.

In some of the present implementations, the public PLMNs and the privatePLMNs may use the same Mobile Country Code (MCC) but different MobileNetwork Codes (MNCs). In some of the present implementations, ifmultiple PLMNs share the same MCC, the cell may transmit both the MCCand the MNC of one of the PLMNs (e.g., via system information and/or viadedicated signaling), and transmit only the MNCs (with an absence of theMCC) of the other PLMNs.

In some of the present implementations, a cell may broadcast theidentification information of one or more PLMNs operating other cells onthe same carrier frequency (e.g., on an unlicensed carrier frequency).For example, the one or more PLMNs may be called as “neighboringPLMN(s).” The UE may read the identification information broadcast bythe cell (e.g., in SIB1 or other System Information (SI)) and obtain thePLMN ID(s) of the neighboring PLMN(s) that operate cells on the samecarrier frequency. The AS entity of the UE may report the found PLMNID(s), including the identification information of PLMNs operating thiscell and PLMNs operating neighboring cells on the same carrierfrequency, to the NAS entity of the UE. The NAS entity of the UE maythen select a PLMN as an outcome of the PLMN selection procedure basedon the reported PLMN ID(s).

In some of the present implementations, the system information from thecell(s) on a carrier frequency (e.g., licensed carrier frequency,unlicensed carrier frequency) may include PLMN type information thatindicates at least one PLMN type (e.g., public, private, or both)associated with the cells. For example, a cell on an unlicensed spectrummay broadcast an indicator to indicate that the cell is shared by publicPLMNs, private PLMNs, or both of the public and private PLMNs. In someof the present implementations, each PLMN ID broadcast by the cell maybe accompanied by an indicator to indicate the PLMN type associated withthe corresponding PLMN ID. For example, the cell may broadcast severalPLMN lists. One PLMN list may include the PLMN IDs of public PLMNs, onePLMN list may include the PLMN IDs of private PLMNs, and one PLMN listmay include the PLMN IDs of both public and private PLMNs.

In some of the present implementations, the cell may broadcast theindicator(s) and the identification information of PLMN(s) (e.g., PLMNID list(s)) via the SIB1 or other SI. If there is no additionalindicator broadcasted by the cell operating on the unlicensed spectrum,the UE may, by default, treat the PLMNs identified by the broadcastidentification information of PLMN(s) (e.g., PLMN ID list) as publicPLMNs. In some of the present implementations, if the UE supports publicPLMNs only, the AS entity of the UE may treat the public PLMN IDsbroadcast by the cell as the candidate available PLMNs. In some of thepresent implementations, if the UE supports private PLMNs only, the ASentity of the UE may treat the private PLMN IDs (e.g., PLMN IDs and/orNIDs, PLMN IDs and/or CAG IDs) broadcast by the cell as the candidateavailable PLMNs. In some of the present implementations, if the UEsupports both public PLMNs and private PLMNs, the AS entity of the UEmay treat both the public PLMN IDs and the private PLMN IDs broadcast bythe cell as the candidate available PLMNs. In some of the presentimplementations, the AS entity of the UE may select the available PLMNsfrom the candidate available PLMNs based on a predefined rule. Forexample, if the signal quality of a cell broadcasting the identificationinformation of one or more candidate available PLMNs fulfills ahigh-quality criterion, the one or more candidate available PLMNs may beselected as the available PLMN(s). The AS entity of the UE may reportthe available PLMN(s) to the NAS entity of the UE for PLMN selection.

In some of the present implementations, on each unlicensed carrierfrequency, the UE may search for the N-strongest cells (e.g., theN1-strongest cells, the N2-strongest cells, the N3-strongest cells, orthe N3′-strongest cells as illustrated in FIGS. 2A, 2B and 6) and readtheir system information, in order to find out which PLMN(s) the cellsbelong to Taking FIG. 2A as an example, where N=N1=3, cells C1, C2 andC3 are the N1-strongest cells that meet the high-quality criterion oncarrier frequency f1. According to the system information of cells C1,C2 and C3, the UE may know that cells C1, C2 and C3 belong to PLMN #1,PLMN #2 and PLMN #3, respectively. In some of the presentimplementations, on each unlicensed carrier, the UE may search for atmost N-strongest cells and read their system information, in order tofind out which PLMN(s) the cells belong to.

In some of the present implementations, the value of N may be predefined(e.g., defined by 3GPP specifications), preconfigured to the UE (e.g.,stored in a USIM and/or stored in a UICC), or configured by cell(s)(e.g., via system information and/or via dedicated signaling),determined based on UE implementation.

In some of the present implementations, the UE may search for theN-strongest cells which supports the UE's PLMN type (e.g., public,private, both), and read their system information. For example, if theUE supports public PLMNs, the UE may search for the N-strongest cellswhich support public PLMNs and read their system information. In such acase, the searched maximum N strongest cells support the UE's PLMN type(e.g., public, private, both).

In some of the present implementations, the UE may search for theN-strongest cells regardless of their supporting PLMN types and readtheir system information. In such a case, the searched N-strongest cellsmay possibly not support the UE's PLMN type. In some of the presentimplementations, if the UE cannot search for the N-strongest cells onthe unlicensed carrier frequency, the UE may turn to search for theX-strongest cells on the unlicensed carrier frequency and read theirsystem information, where X is a positive integer smaller than N. Thevalue of X may be preconfigured or left for UE implementations.

In some of the present implementations, the search for PLMNs may bestopped/modified (e.g., change the N or X value) on request from the NASentity of the UE. The UE may optimize the PLMN search upon theN-strongest cells and/or X-strongest cells by using the storedinformation (e.g., information of carrier frequencies) and optionallyalso the information of the cell parameters from previously receivedmeasurement control information elements.

In some of the present implementations, the UE may measure the channeloccupancy ratio of all carrier frequencies. The UE may select thecarrier frequency with the lowest channel occupancy ratio and read thesystem information of cells on the selected carrier frequency.

If the UE reads one or more PLMN IDs in each of the N-strongest cells,each found PLMN may be reported to the NAS entity of the UE as the highquality PLMN(s). In some of the present implementations, if the UE readsone or more PLMN IDs in each of the N-strongest cells, each found PLMN,which belongs to the PLMN type supported by the UE (e.g., public,private, or both), may be reported to the NAS entity of the UE as thehigh quality PLMN(s). In such cases, the found PLMN(s) to be reported tothe NAS entity of the UE may be regarded as the available PLMN(s)reported by the AS entity of the UE to NAS entity of the UE.

In some of the present implementations, the high-quality criterion forfinding the N-strongest cells may be fulfilled if the measured metricvalue of a cell is greater than, or equal to, a threshold value (e.g.,−110 dBm). The measured metric value may be at least one of a RSRPvalue, a RSRQ value, a Received Signal Strength Indicator (RSSI) value,a Signal to Interference-plus-Noise Ratio (SINR) value, and a channeloccupancy ratio value. The threshold value may be predefined,preconfigured, or configured by the cell through the system information(e.g., via the SIB1 or other SI) or dedicated signaling (e.g., via RRCmessages). For example, the measured RSRP value may be greater than orequal to a threshold value, e.g., −110 dBm. If the system informationand the dedicated signaling are adopted, the threshold value may bestored by the UE and used in a later PLMN selection procedure. Forexample, the UE may use the stored threshold value given by the SI ordedicated signaling for the PLMN selection. Whether a cell is “strong”or not may depend on the measured metric value of the cell. For example,if the RSRP value is used as the measured metric value, the UE maycreate a cell list for an unlicensed carrier frequency according to theorder of RSRP values of the cells on the unlicensed carrier frequency.For example, the cell list may include cell IDs (or other identificationinformation of the cells) which are ordered by their correspondingcells' measured metric values, from the highest measured metric value tothe lowest measured metric value. In some of the presentimplementations, the UE may measure an unlicensed carrier frequency or alicensed carrier frequency for a time period (Tm). The value of Tm maybe predefined, preconfigured, or depend on UE implementation. If Tm isnot configured to the UE, a default value for Tm may be adopted. In someof the present implementations, Tm may be dynamically configured by thecell via the system information (e.g., the SIB1 or other SI) or thededicated signaling (e.g., via RRC messages) to the UE. In some of thepresent implementations, the measured metric value may be obtained frommeasurements during the time period Tm. In some of the presentimplementations, the measured metric value may be obtained by averaginga set of measured metric values sampled in the time period Tm.

In some of the present implementations, if the N-strongest cells fulfillthe high-quality criterion, the AS entity of the UE may report theidentification information of PLMNs (e.g., PLMN ID(s), PLMN ID(s) and/orNID(s), PLMN ID(s) and/or CAG ID(s)) found from the broadcast systeminformation by the N-strongest cells to the NAS entity of the UE,without reporting the measured metric value(s). In some of the presentimplementations, when the N-strongest cells fulfill the high-qualitycriterion, the AS entity of the UE may report the identificationinformation of PLMNs (e.g., PLMN ID(s), PLMN ID(s) and/or NID(s), PLMNID(s) and/or CAG ID(s)) found from the broadcast system information bythe N-strongest cells and the measured metric values of the N-strongestcells to the NAS entity of the UE. In some of the presentimplementations, when the N-strongest cells do not fulfill thehigh-quality criterion but the UE has detected the identificationinformation of PLMNs (e.g., PLMN ID(s), PLMN ID(s) and/or NID(s), PLMNID(s) and/or CAG ID(s)) from the broadcast system information by theN-strongest cells, the AS entity of the UE may report the detectedidentification information of PLMNs and the measured metric values ofthe N-strongest cells to the NAS entity of the UE. In some of thepresent implementations, the measured metric value of each PLMN found onthe same N-strongest cells may be the same. In some of the presentimplementations, the measured metric value of each PLMN found on theN-strongest cells that does not fulfill the high-quality criterion maybe the same.

In some of the present implementations, if the number of cellsfulfilling the high-quality criterion is greater than, or equal to, 1but less than N, the AS entity of the UE may report the identificationinformation of PLMNs found on the cells fulfilling the high-qualitycriterion to the NAS entity of the UE. In some of the presentimplementations, if the number of cells fulfilling the high-qualitycriterion is greater than, or equal to, 1 but less than N, the AS entityof the UE may report the identification information of PLMNs found onthe cells not fulfilling the high-quality criterion, and the measuredmetric value of each PLMN found on the cells not fulfilling thehigh-quality criterion, to the NAS entity of the UE. In some of thepresent implementations, if the number of cells fulfilling thehigh-quality criterion is zero, the AS entity of the UE may report theidentification information of PLMNs found on the N-strongest cellstogether with the corresponding measured metrics of the N-strongestcells. In some of the present implementations, if the ranking of themeasured metric value of a cell is in the top N but the UE cannot readany PLMN ID from this cell, the UE may not consider such a cell as oneof the N-strongest cells. In some of the present implementations, the UEmay then store the information (e.g., the relative cell ID) of the celland take it into account for a further cell (re)selection in which thecell may be given a lower priority to be selected as a suitable cellthan other cells. The UE may remove the information (e.g., the relativecell ID) of the cell after the cell selection procedure, after a cellreselection procedure, or after a period of time.

In some of the present implementations, the AS entity of the UE mayselect a PLMN as the outcome of the PLMN selection procedure. This typeof PLMN selection procedure may be referred to as a procedure of PLMNselection by UE AS.

In some of the present implementations, during the procedure of PLMNselection by UE AS, the NAS entity of the UE may provide a potentialPLMN list to the AS entity of the UE. The potential PLMN list mayinclude at least one PLMN-related ID. In some implementations, thePLMN-related ID(s) may be PLMN ID(s), SNPN ID(s), or PNI-NPN ID(s). TheSNPN ID(s) may include PLMN ID(s) and/or NID(s). The PNI-NPN ID(s) mayinclude PLMN ID(s) and/or CAG ID(s).

The AS entity of the UE may select one or more PLMN-related IDs from thepotential PLMN list and report the selected PLMN-related ID(s) in aselected PLMN list to the NAS entity of the UE. In some of the presentimplementations, the AS entity of the UE may inform the NAS entity ofthe UE of the selected PLMN-related ID(s) by reporting the index(ices)of the potential PLMN list(s). In some of the present implementations,if the AS entity of the UE cannot select any PLMN-related ID from thepotential PLMN list, the AS entity of the UE may report a default valueto the NAS entity of the UE to indicate the selected PLMN. In some ofthe present implementations, the selected PLMN's PLMN-related ID may bein the beginning (or in the end) of the selected PLMN list.

In some of the present implementations, the search for PLMNs may bestopped once the AS entity of the UE has selected a PLMN. In some of thepresent implementations, the search for PLMNs may be stopped once the ASentity of the UE has found the N-strongest cells. In some of the presentimplementations, the PLMN IDs broadcast by the N-strongest cells may notmatch the potential PLMN list. In some of the present implementations,one or more PLMN IDs broadcast by the N-strongest cells may match thepotential PLMN list and the AS entity of the UE may select the PLMN(s)which matches the potential PLMN list. In some of the presentimplementations, the search for PLMNs may be stopped once the AS entityof the UE has found all cells that fulfill the high-quality criterion orthe N-strongest cells that fulfill the high-quality criterion.

In some of the present implementations, the PLMN-related ID of theselected PLMN by the AS entity of the UE may be broadcast by one or moreof the N-strongest cells via the SIB1 or other SI. In such a case, theN-strongest cells may fulfill the high-quality criterion. In some of thepresent implementations, the AS entity of the UE may select the PLMNwith its PLMN-related ID being broadcast by the most cells that fulfillthe high-quality criterion. These cells may be operated in theintra-frequency or in the inter-frequency. In some of the presentimplementations, the AS entity of the UE may select the PLMN with itsPLMN-related ID being broadcast by the most cells for which the UE hasbeen able to read the PLMN-related IDs. In some of the presentimplementations, the AS entity of the UE may select the PLMN with itsPLMN-related ID being broadcast by the cell which has the strongestmeasured metric value among cells broadcasting the UE's potential PLMNlist.

In some of the present implementations, if the NAS entity of the UEverifies/approves the PLMN selected by the AS entity of the UE, the NASentity of the UE may provide a positive indicator to the AS entity ofthe UE. After receiving the positive indicator, the AS entity of the UEmay perform the cell selection procedure to select a suitable cellbelonging to the selected PLMN to camp on. Conversely, if the NAS entityof the UE fails to verify (or rejects) the selected PLMN, the NAS entityof the UE may provide a negative indicator to the AS entity of the UE.After receiving the negative indicator, the AS entity of the UE maytrigger the PLMN selection procedure. In some of the presentimplementations, after receiving the negative indicator, the AS entityof the UE may bar the reported PLMN for a period of time to avoidselecting it again. In some of the present implementations, afterreceiving the negative indicator, the AS entity of the UE may reportanother PLMN in the selected PLMN list to the NAS entity of the UE. Ifno other PLMN is in the selected PLMN list, the AS entity of the UE maytrigger the PLMN selection procedure. In some of the presentimplementations, if the NAS entity of the UE fails to verify (orrejects) the selected PLMN, the NAS entity of the UE may select a PLMNfrom the selected PLMN list by itself. In some of the presentimplementations, the NAS entity of the UE may indicate to the AS entityof the UE which PLMN is selected, if the NAS entity of the UE selectsthe PLMN.

In some of the present implementations, the AS entity of the UE mayselect a PLMN and report a selected PLMN list to the NAS entity of theUE. The selected PLMN list may include the selected PLMN'sidentification information (e.g., the PLMN-related ID(s) of the selectedPLMN(s)). For example, the PLMN-related ID of the selected PLMN may be,by default, arranged in the first or last entry of the selected PLMNlist. In some of the present implementations, an indicator may be usedin the selected PLMN list to mark the selected PLMN. In some of thepresent implementations, once the AS entity of the UE confirms that theselected PLMN has been verified by the NAS entity of the UE (e.g., theAS entity of the UE reports a selected PLMN to the NAS entity of the UE,and then receives a positive indicator from the NAS entity of the UE),the UE may perform the cell selection procedure to select a suitablecell belonging to the selected PLMN to camp on. In some of the presentimplementations, the suitable cell may fulfill the high-qualitycriterion. In some of the present implementations, if the cell where theUE receives the PLMN ID of the selected PLMN does not fulfill thehigh-quality criterion, the UE may perform the cell (re)selectionprocedure to find another cell as the suitable cell (e.g., the UE doesnot directly select such cell as the suitable cell).

After PLMN selection, the UE may perform a cell selection procedure tofind out a suitable cell belonging to the selected PLMN on a carrierfrequency. In some of the present implementations, the UE may performmeasurements for cell selection and reselection purposes.

The NAS entity of the UE may control the RAT(s). For example, during thecell selection procedure, the NAS entity of the UE may request the ASentity of the UE to perform measurements on an unlicensed spectrum(e.g., including one or more unlicensed carrier frequencies) for theunlicensed RAT(s) (e.g., NR-U). The NAS entity of the UE may indicatethe RAT(s) associated with the selected PLMN (e.g., equivalent PLMN(s)or registered PLMNs) to the AS entity of the UE. In some of the presentimplementations, the NAS entity of the UE may maintain at least one of alist of forbidden registration area(s) and a list ofequivalent/registered PLMN(s). In some of the present implementations,the NAS entity of the UE may define the range of forbidden registrationarea(s) by GPS coordination. The UE may select a suitable cell based onthe RRC_IDLE or RRC_INACTIVE state measurements and the cell selectioncriteria. In some of the present implementations, the UE may utilize theRRC_CONNECTED state measurements for cell (re)selection.

In unlicensed carrier frequencies, because multiple PLMNs may possiblyuse the same carrier frequency without any coordination, the best cellfound by a UE on an unlicensed carrier frequency may not belong theselected/registered/equivalent PLMN. In some of the presentimplementations, the UE may select a non-best cell on the unlicensedcarrier frequency as a suitable cell to camp on, if the best cell doesnot belong to the selected/registered/equivalent PLMN. In some of thepresent implementations, the non-best cell may have a better receivedradio signal quality than other cells belonging to theselected/registered/equivalent PLMN. Taking FIG. 2B as an example, thebest cell C1 does not belong to the selected PLMN #2, so the UE may skipcell C1 and select the next-best cell C2 (which belongs to the selectedPLMN #2) as the suitable cell to camp on. In addition, cell C2 may havea better received radio signal quality than other cells belonging to theselected PLMN #2 (e.g., cell CK).

In some of the present implementations, for an initial cell selection,the UE may scan all Radio Frequency (RF) channels in the unlicensedbands according to its capabilities to find a suitable cell, if the UEis indicated to utilize the unlicensed RAT(s). On each carrier frequencywithin an unlicensed spectrum, the UE may read the system information ofthe cells and search for the strongest cell belonging to the UE'sselected/registered/equivalent PLMN. That is, among all cells in eachcarrier frequency which broadcast the identification information of theUE's selected/registered/equivalent PLMN, the UE may find the strongestone as the suitable cell. Conversely, among all cells in each carrierfrequency, a cell (e.g., cell C1 illustrated in FIG. 2B) that does notbroadcast the selected/registered/equivalent PLMN's identificationinformation may not be selected as the suitable cell, even if the cellhas a better received radio signal quality than other cells.

In some of the present implementations, the UE may be configured with athreshold value. The threshold value may be preconfigured or broadcastby the cells. In some of the present implementations, the thresholdvalue may be a cell-specific threshold value that is broadcast by eachcell. Such a cell-specific threshold value may be applied to thecorresponding cell to determine whether the cell has a good signalquality to be selected as a suitable cell. For example, on each carrierfrequency, the UE may search for the cells with their measured metricvalues above the threshold value. Among the searched cells, the UE mayfind a suitable cell. As illustrated in FIG. 2B, each of cells C1, C2,C3 on carrier frequency f1 may have a measured metric value above thethreshold value. Among cells C1, C2, C3, the UE may consider cell C2 asthe suitable cell because it belongs to the selected PLMN #2.

In some of the present implementations, the UE may require theinformation of carrier frequencies, which the UE may receive frommeasurement control information elements of a camped/serving cell and/orfrom the system information of a camped/serving/detected cell, forperforming cell (re)selection procedures. In some of the presentimplementations, the UE may require the information of cell parameters,which the UE may receive from measurement control information elementsof a camped/serving cell and/or from the system information of acamped/serving/detected cells, for performing cell (re)selectionprocedures. In some of the present implementations, if a cell does notbroadcast the threshold value, the UE may always treat the cell as asuitable cell. For example, the UE may assume that the threshold valuefor the cell is negative infinity. In some of the presentimplementations, if a cell does not broadcast the threshold value, theUE may use a default threshold value to perform the comparison betweenthe received signal quality and the threshold value. In some of thepresent implementations, the threshold value broadcast by a cell may beset to positive infinity when the cell bars all UEs. In some of thepresent implementations, the UE may set the threshold value for a cellto be positive infinity when the UE bars the corresponding cell.

In some of the present implementations, on each carrier frequency, theUE may search for the cells that satisfy the following two conditions:(1) such cells belong to the UE's selected/registered/equivalent PLMN,and (2) the measured metric values of such cells are above a thresholdvalue. Among the searched cells on each frequency, the UE may select thestrongest one (e.g., with the best measured metric value) as thesuitable cell. In some of the present implementations, once the UE findsa cell that satisfies the above two conditions, the UE may directlyselect the cell as the suitable cell if the cell is not barred to theUE.

In some of the present implementations, the UE may use the cellselection criterion S to find the suitable cell. In some of the presentimplementations, the cell selection criterion S may be different betweena licensed spectrum and an unlicensed spectrum. For example, for a cellselection procedure on the licensed spectrum, the cell selectioncriterion S in a normal coverage may be fulfilled when:

Srxlev>0 and Squal>0,

where:

Srxlev=Q _(rxlevmeas)−(Q _(rxlevmin) +Q _(rxlevminoffset))−P_(compensation) −Qoffset_(temp), and

Squal=Q _(qualmeas)−(Q _(qualmin) −Q _(qualminoffset))−Qoffset_(temp)

where:

Srxlev Cell selection Receive (RX) level value (dB) Squal Cell selectionquality value (dB) Qoffset_(temp) Offset temporarily applied to a cell(dB) Q_(rxlevmeas) Measured cell RX level value (RSRP) Q_(qualmeas)Measured cell quality value (RSRQ) Q_(rxlevmin) Minimum required RXlevel in the cell (dB m). If the UE supports Supplementary Uplink (SUL)frequency for this cell, Qrxlevmin is obtained from q-RxLevMin- sul, ifpresent, in SIB1, SIB2 and SIB4, additionally, ifQ_(rxlevminoffsetcellSUL) is present in SIB3 and SIB4 for the concernedcell, this cell specific offset is added to the corresponding Qrxlevminto achieve the required minimum RX level in the concerned cell; elseQrxlevmin is obtained from q-RxLevMin in SIB1, SIB2 and SIB4,additionally, if Q_(rxlevminoffsetcell) is present in SIB3 and SIB4 forthe concerned cell, this cell specific offset is added to thecorresponding Qrxlevmin to achieve the required minimum RX level in theconcerned cell. Q_(qualmin) Minimum required quality level in the cell(dB). Additionally, if Q_(qualminoffsetcell) is signaled for theconcerned cell, this cell specific offset is added to achieve therequired minimum quality level in the concerned cell. Q_(rxlevminoffset)Offset to the signaled Q_(rxlevmin) taken into account in the Srxlevevaluation as a result of a periodic search for a higher priority PLMNwhile camped normally in a Visited PLMN (VPLMN) Q_(qualminoffset) Offsetto the signaled Q_(qualmin) taken into account in the Squal evaluationas a result of a periodic search for a higher priority PLMN while campednormally in a VPLMN P_(compensation) If the UE supports theadditionalPmax in the NS-PmaxList, if present, in SIB1, SIB2 and SIB4:max(P_(EMAX1) − P_(PowerClass), 0) − (min(P_(EMAX2), P_(PowerClass)) −min(P_(EMAX1), P_(PowerClass))) (dB); else: max(P_(EMAX1) −P_(PowerClass), 0) (dB) P_(EMAX1), Maximum TX power level of a UE mayuse when transmitting on the uplink in P_(EMAX2) the cell (dBm) definedas P_(EMAX). If UE supports SUL frequency for this cell, P_(EMAX1) andP_(EMAX2) are obtained from the p-Max for SUL in SIB1 and NR-NS-PmaxList for SUL respectively in SIB1, SIB2 and SIB4, else P_(EMAX1) andP_(EMAX2) are obtained from the p-Max and NR-NS-PmaxList respectively inSIB1, SIB2 and SIB4 for normal UL. P_(PowerClass) Maximum RF outputpower of the UE (dBm) according to the UE power class.

In some of the present implementations, other criteria may be applied tothe unlicensed spectrum operations. For example, an SINR value may be ameasured metric value. The UE may compare the signal strength from acell with the interference caused from other cells. In some of thepresent implementations, the SINR value may be defined by aSynchronization Signal (SS)-SINR (SS-SINR) value. For example, theSS-SINR value may be defined as (but not limited to) the linear averageover the power contribution (in [W]) of the resource elements carrying(secondary) SSs divided by the linear average of the noise andinterference power contribution (in [W]) over the resource elementscarrying (secondary) SSs within the same frequency bandwidth. In some ofthe present implementations, the time resource(s) for measuring theSS-SINR value may be confined within an SS/Physical Broadcast Channel(PBCH) Block Measurement Time Configuration (SMTC) window duration. TheUE may receive the SMTC for measuring a cell via dedicated signaling orsystem information from this cell or other cells.

In some of the present implementations, the SINR value of a cell may begreater than, or equal to, a threshold (e.g., S_(SINR)>0,S_(SINR)=Q_(SINR)−Q_(SINR_th)+R_(SINR)). S_(SINR) may be the S criterionassociated to the SINR value. Q_(SINR) may be the measured cell RX SINRvalue (dB). Q_(SINR_th) may be the threshold associated to the SINRvalue. R_(SINR) may be the remainder items if necessary. Each item mayeither be broadcast by the cell to the UE, be unicast via dedicatedsignaling by the cell, or be preconfigured to the UE (e.g., stored in aUSIM and/or stored in a UICC). In some of the present implementations,R_(SINR) may be zero. Q_(SINR_th) may be preconfigured or broadcast inthe Master Information Block (MIB) or SIB1 from the cell. Q_(SINR_th)may be cell-specific or unique for the system. For example, ifQ_(SINR_th) is cell-specific, it may be applied to the cell whichbroadcasts the Q_(SINR_th) value.

For cell selection procedures under multi-beam operations, the averageSINR among beams of a cell may be considered. For example, thebeam-average SINR of a cell may be greater than, or equal to, athreshold (e.g., S_(SINR_av)>0,S_(SINR_av)=Q_(SINR_av)−Q_(SINR_th_av)+R_(SINR_av)). S_(SINR_av) may bethe S criterion associated to the beam-average SINR. Q_(SINR_av) may bethe beam-average SINR of a cell. Q_(SINR_th_av) may be the thresholdassociated with the beam-average SINR. R_(SINR_av) may be the remainderitems if necessary. Each item may either be broadcast by the cell to theUE, be unicast via dedicated signaling by the cell, or be preconfiguredto the UE (e.g., stored in a USIM and/or stored in a UICC). In some ofthe present implementations, R_(SINR_av) may be zero. Q_(SINR_th_av) maybe cell-specific or unique for the system. If Q_(SINR_th) iscell-specific, it may be applied to the cell which broadcasts theQ_(SINR_th) value.

In some of the present implementations, the UE may derive an SINR valuefor a beam. Thus, for each beam, there may be an SINR value. There aremany approaches to define the beam-specific SINR. For example, if thereare “B” beams, Q_(SINR_th_av) may be derived by the summation of allbeam-specific SINR values divided by “B.” In another example, if thereare “B” beams, Q_(SINR_th_av) may be derived by the summation of allreceived signals of beams divided by the summation of all interferenceand noise of all beams. The measurement quantity may be the SS/PBCHblock of the cell. Each SS/PBCH block of the cell may correspond to abeam. The value of “B” may be a positive integer.

In some of the present implementations, a threshold (e.g.,Q_(SINR_Beam_th)) may be configured. Only the beams with an SINR valueabove the threshold (e.g., Q_(SINR_Beam_th)) may be used for derivationof the beam-average SINR value. For example, if there are “B1” beamswith their SINR values above the threshold (e.g., Q_(SINR_Beam_th)),Q_(SINR_th_av) may be derived by the summation of the B1 beam-specificSINR values divided by “B1.” In some of the present implementations, ifthere are “B1” beams, Q_(SINR_th_av) may be derived by the summation ofall received signals of beams divided by the summation of allinterference and noise of all beams. If there are no beams with theirbeam-specific SINR values above the threshold (e.g., Q_(SINR_Beam_th)),the highest SINR value among the beams may be used for the S criterion.For example, the highest SINR value among the beams may be used asQ_(SINR_av). In some of the present implementations, if “B1” is higherthan, or equal to, another value “B2,” only the SINR values of the B2beams may be used to derive the beam-average SINR value. For example,the highest “B2” SINR values among the “B1” SINR values may be used. Inanother example, the lowest “B2” SINR values among the “B1” SINR valuesmay be used. In still another example, the “B2” SINR values may berandomly selected from the “B 1” SINR values. In some of the presentimplementations, the “B2” value may be preconfigured or broadcast by thecell. The “B2” value may be sent by the cell via dedicated signaling. Onthe other hand, the “Q_(SINR_Beam_th)” value may be preconfigured orbroadcast by the cell to the UE. The “Q_(SINR_Beam_th)” value may besent by the cell via the dedicated signaling. The values of “B1” and“B2” may be positive integers.

In some of the present implementations, the carrier frequency bandwidthfor the RAT on an unlicensed spectrum (e.g., NR-U) may be (but notlimited to) 20 MHz. If wideband is considered, the carrier frequency forthe RAT on the unlicensed spectrum may be a multiple of 20 MHz. Forexample, an unlicensed carrier frequency may have a channel bandwidth of100 MHz. For another example, a 100 MHz bandwidth may be divided intofive different unlicensed carrier frequencies, with each having achannel bandwidth of 20 MHz.

In some of the present implementations, the cell reselection procedureon an unlicensed spectrum (e.g., NR-U) may consider the (reselection)priority and ranks. In some of the present implementations, absolutepriorities of different NR frequencies, different NR-U frequencies orinter-RAT frequencies may be provided to the UE in the systeminformation (e.g., SIB1, SIB2, SIB3, SIB4, SIB5), in the dedicatedsignaling (e.g., RRC (Connection) Release message, RRC (Connection)Release message with suspend configuration, RRC (Connection) Releasemessage without suspend configuration), or by inheriting from anotherRAT during the inter-RAT cell (re)selection. In some of the presentimplementations, in the case of system information, the NR frequency,the NR-U frequency or the inter-RAT frequency may be listed withoutproviding a priority (e.g., the field cellReselectionPriority may beabsent for that frequency). If the priorities are provided in thededicated signaling (e.g., RRC (Connection) Release message, RRC(Connection) Release message with suspend configuration, RRC(Connection) Release message without suspend configuration), the UE mayignore all the priorities provided in system information.

In some of the present implementations, if the NR and the NR-U areconsidered as the same RAT, the NR frequency and the NR-U frequency maybe inter-frequencies. In some of the present implementations, if the NRand the NR-U are considered as different RATs, the NR frequency and theNR-U frequency may be inter-RAT frequencies. In some of the presentimplementations, different unlicensed carrier frequencies for the sameRAT (e.g., NR-U) may be considered as inter-frequencies.

In some of the present implementations, the cell may broadcast thepriority information (e.g., inter-RAT frequency priority and/orinter-frequency priority). For example, the priority information may beincluded in the SIB1 and/or other SI (e.g., the SIB2, the SIB3, theSIB4, and the SIB5). The cell may inform the UE of the priorityinformation via the dedicated signaling (e.g., an RRC Release message).In some of the present implementations, different RATs may havedifferent priorities (e.g., RAT-specific priority). In some of thepresent implementations, different carrier frequencies may havedifferent priorities, e.g., frequency-specific priority. For example,for an E-UTRA RAT, the frequency priority information may include thecarrier frequency of E-UTRA, the cell reselection priority correspondingto the carrier frequency, and optionally the cell reselectionsub-priority. For an NR RAT, the frequency priority information mayinclude the carrier frequency of NR, the cell reselection prioritycorresponding to the carrier frequency, and optionally the cellreselection sub-priority corresponding to the carrier frequency. For anNR-U RAT, the frequency priority information may include the carrierfrequency of NR-U, the cell reselection priority corresponding to thecarrier frequency, and optionally the cell reselection sub-prioritycorresponding to the carrier frequency. In some of the presentimplementations, the frequency priority information of NR RAT mayinclude the carrier frequency of NR-U RAT, the cell reselection prioritycorresponding to the carrier frequency, and optionally the cellreselection sub-priority corresponding to the carrier frequency.

In some of the present implementations, based on the measurementresults, the UE may rank the serving cell and the non-serving cells(e.g., intra-frequency cells, inter-frequency cells and inter-RATcells). For the RAT on an unlicensed spectrum (e.g., NR-U), theintra-frequency cells may belong to the same PLMN as that of the servingcell, or belong to different PLMNs from that of the serving cell.Similarly, for the RAT on the unlicensed spectrum (e.g., NR-U), theinter-frequency cells may belong to the same PLMN as that of the servingcell, or different PLMNs from that of the serving cell. In some of thepresent implementations, the UE may rank the serving cell and thenon-serving cells (e.g., intra-frequency cells, inter-frequency cellsand inter-RAT cells) belonging to the same PLMN as that of the servingcell. In some of the present implementations, the UE may rank theserving cell and the non-serving cells (e.g., intra-frequency cells,inter-frequency cells, inter-RAT cells), which may not exactly belong tothe same PLMN as that of the serving cell.

In some of the present implementations, the RAT on an unlicensedspectrum may be another RAT compared to the RATs on a licensed spectrum.For example, the NR-U having a PCell on an unlicensed spectrum may be aRAT different from the NR (which may be assumed to have a PCell on alicensed spectrum). For example, the E-UTRA on a licensed spectrum maybe another RAT compared to NR-U operating on an unlicensed spectrum. Insome of the present implementations, the inter-RAT information mayinclude the E-UTRA specific information, the NR specific information,and NR-U specific information.

In some of the present implementations, when evaluating Srxlev and Squalof non-serving cells for cell reselection purposes, the UE may useparameters provided by the serving cell. Some rules may be used by theUE to limit required measurements. In some of the presentimplementations, if the serving cell fulfills Srxlev >S_(IntraSearchP)and Squal >S_(IntrasearchQ), the UE may choose not to performintra-frequency measurements. Otherwise, the UE may performintra-frequency measurements. S_(IntrasearchP) may be the Srxlevthreshold (in dB) for intra-frequency measurements, for example, interms of RSRP. S_(IntrasearchQ) may be the Squal threshold (in dB) forintra-frequency measurements, for example, in terms of RSRQ. In some ofthe present implementations, if the serving cell fulfilsS_(SINR)>S_(IntrasearchSINR), the UE may choose not to performintra-frequency measurements. Otherwise, the UE may performintra-frequency measurements. S_(IntraSearchSINR) may be the threshold(in dB) for intra-frequency measurements, for example, in terms of SINR.In some of the present implementations, if the serving cell fulfilsS_(SINR_av)>S_(IntraSearchSINR_av), the UE may choose not to performintra-frequency measurements. Otherwise, the UE may performintra-frequency measurements. S_(IntrasearchSINR_av) may be thethreshold (in dB) for intra-frequency measurements, for example, interms of average SINR. If multi-beam operation on the unlicensedspectrum is used, S_(IntraSearchSINR_av) may be configured.

Some rules may be required for an inter-frequency cell reselectionprocedure on the unlicensed spectrum(s). In some of the presentimplementations, for an unlicensed inter-frequency with a reselectionpriority higher than the reselection priority of the current frequency,the UE may perform measurements on the unlicensed inter-frequency. Thecurrent frequency may be an unlicensed carrier frequency or a licensedcarrier frequency. The format of the cell reselection priority indicatormay be N bits corresponding to a 2^(N) value. For example, the cellreselection priority indicator may mean the lowest priority when itsvalue is 0. In addition, a higher value of the cell reselectionindicator may correspond to a higher cell reselection priority. In someof the present implementations, a cell reselection sub-priority valuemay be added to the value of the cell reselection priority indicator forthe corresponding frequency or RAT. That is, the cell reselectionsub-priority value and the value of the cell reselection priorityindicator may constitute an absolute priority value for the concernedRAT, or constitute an absolute priority value for the concerned carrierfrequency of the corresponding RAT. In some of the presentimplementations, if the dedicated signaling (e.g., the RRC (Connection)Release message, RRC Release message with suspend configuration, RRCRelease message without suspend configuration) does not include the cellreselection priority indicator, the UE may apply the cell reselectionpriority indicator broadcast in the system information. In some of thepresent implementations, if the system information does not include thecell reselection priority indicator, the UE may apply the stored cellreselection priority indicator. In some of the present implementations,if the dedicated signaling and the system information do not include thecell reselection priority indicator for the corresponding RAT/frequency,and the UE does not store any cell reselection priority indicator forthe corresponding RAT/frequency, the UE may apply a default value as thecell reselection priority indicator for the corresponding RAT/frequency.In some of the present implementations, the default value may be zero,which means that the corresponding RAT/frequency may have the lowestpriority. In some of the present implementations, if the dedicatedsignaling and the system information do not include the cell reselectionpriority indicator for the corresponding RAT/frequency and the UE doesnot store any cell reselection priority indicator for the correspondingRAT/frequency, the UE may treat the cells on the correspondingRAT/frequency as barred during the cell reselection procedure. Forinter-frequency measurements, at least one of the SINR value, the RSSIvalue and the channel occupancy ratio value may be used as the measuredmetrics. For example, the UE may perform measurements on cells indifferent frequencies based on the SINR values, the average SINR values,the RSSI values or the channel occupancy ratio values. For example, theUE may perform measurements on the frequencies based on the RSSI valuesor the channel occupancy ratio values. In some of the presentimplementations, the UE may deprioritize a carrier frequency to beselected in the cell reselection procedure if the measurement results(e.g., the RSSI values or the channel occupancy ratio values) of such acarrier frequency is worse than the measurement results of anotherfrequency with a lower (reselection) priority.

In some of the present implementations, for an unlicensedinter-frequency with a reselection priority equal to or lower than thereselection priority of the current frequency, if the serving cellfulfils Srxlev >S_(nonIntraSearchP) and Squal >S_(nonIntraSearchQ), theUE may decide not to perform measurements on the unlicensedinter-frequencies. In some of the present implementations, if theserving cell fulfils Srxlev >S_(nonIntraSearchSINR), the UE may decidenot to perform measurements on the unlicensed inter-frequencies (with areselection priority equal to or lower than the reselection priority ofthe current frequency). S_(nonIntraSearchSINR) may be a threshold (indB) for unlicensed inter-frequency measurements, for example, in termsof SINR. In some of the present implementations, if the serving cellfulfils Srxlev >S_(nonIntraSearchSINR_av), the UE may decide not toperform measurements on the unlicensed inter-frequencies (with areselection priority equal to or lower than the reselection priority ofthe current frequency). S_(nonIntraSearchSINR_av) may be a threshold (indB) for unlicensed inter-frequency measurements, for example, in termsof average SINR. If the multi-beam operation on an unlicensed spectrumis used, S_(nonIntraSearchSINR_av) may be configured. In some of thepresent implementations, if the conditions are not fulfilled, the UE mayperform measurements of the unlicensed inter-frequencies.

In some of the present implementations, if the measured metric value(e.g., the RSSI value or the channel occupancy ratio value) of thecurrent frequency is above a threshold, the UE may not performmeasurements on the unlicensed inter-frequencies, regardless of thepriority of the unlicensed inter-frequencies. The threshold may beconfigured by the system information or dedicated signaling.

In some of the present implementations, a UE (e.g., in RRC_CONNECTEDstate) may report the measurement results (e.g., the RSSI value or thechannel occupancy ratio value) of different frequencies (e.g., in theunlicensed spectrum(s) or the licensed spectrum(s)) to the serving cellvia the dedicated signaling (e.g., Measurement Report message). Uponreceiving the measurement results, the serving cell may adjust the(reselection) priority of different frequencies. Thus, the cell may sendthe updated (reselection) priority of different frequencies in thesystem information (e.g., in the SIB1, the SIB2, the SIB3, the SIB4, orthe SIB5) or in the dedicated signaling (e.g., in an RRC (Connection)Release message, in an RRC Release message with suspend configuration,in an RRC Release message without suspend configuration) to the UE. Uponacquiring the updated (reselection) priority, the UE may replace thestored value of (reselection) priority with the updated (reselection)priority for cell reselection.

Some rules may be required for the inter-RAT frequency cell reselectionbetween the unlicensed spectrum(s) and the licensed spectrum(s). In someof the present implementations, if the inter-RAT frequency isunlicensed, each unlicensed carrier frequency may correspond to areselection priority. In some of the present implementations, if theinter-RAT frequency is unlicensed, all unlicensed carrier frequenciesmay correspond to a reselection priority.

In some of the present implementations, if an unlicensed inter-RATfrequency (e.g., an NR-U frequency) has a reselection priority higherthan the reselection priority of the current licensed carrier frequency(e.g., an NR frequency or an E-UTRA frequency), the UE may performmeasurements on the unlicensed inter-RAT frequency. In some of thepresent implementations, if at least one licensed inter-RAT frequency(e.g., an NR frequency or an E-UTRA frequency) has a reselectionpriority higher than the reselection priority of the current licensedcarrier frequency (e.g., an NR frequency or an E-UTRA frequency), the UEmay not perform measurements on the unlicensed inter-RAT frequency.

In some of the present implementations, if the licensed inter-RATfrequency (e.g., an NR frequency or an E-UTRA frequency) has areselection priority higher than the reselection priority of the currentunlicensed carrier frequency (e.g., an NR-U frequency), the UE mayperform measurements of the licensed inter-RAT frequency having thehigher reselection priority.

In some of the present implementations, if the measured metric value ofthe current unlicensed carrier frequency (e.g., the SINR value, the RSSIvalue or the channel occupancy ratio value) is below a threshold, the UEmay perform measurements on the licensed inter-RAT frequencies (e.g., anNR frequency or an E-UTRA frequency). In some of the presentimplementations, the threshold of the corresponding measured metricvalue may be configured in the system information or in the dedicatedsignaling, from the cell to the UE.

In some of the present implementations, for an unlicensed inter-RATfrequency with a reselection priority equal to or lower than thereselection priority of the current licensed carrier frequency, if theserving cell fulfills Srxlev >S_(nonIntraSearchP) and Squal>S_(nonIntraSearchQ), the UE may choose not to perform measurements onthe unlicensed inter-RAT frequencies. S_(nonIntraSearchP) may be thethreshold (in dB) for the unlicensed inter-RAT frequency measurement,for example, in terms of RSRP. S_(nonIntraSearchQ) may be the threshold(in dB) for the unlicensed inter-RAT frequency measurement, for example,in terms of RSRQ.

In some of the present implementations, for a licensed inter-RATfrequency with a reselection priority equal to or lower than thereselection priority of the current unlicensed carrier frequency, if theserving cell fulfills a condition of Srxlev >S_(nonIntraSearchP) andSqual >S_(nonIntraSearchQ), the UE may choose not to performmeasurements on the licensed inter-RAT frequency. In some of the presentimplementations, for a licensed inter-RAT frequency with a reselectionpriority equal to or lower than the reselection priority of the currentunlicensed carrier frequency, if the serving cell fulfills a conditionof Srxlev >S_(nonIntraSearchSINR), the UE may choose not to performmeasurements on the licensed inter-RAT frequency. S_(nonIntraSearchSINR)may be the threshold (in dB) for the licensed inter-RAT frequencymeasurement, for example, in terms of SINR. In some of the presentimplementations, for a licensed inter-RAT frequency with a reselectionpriority equal to or lower than the reselection priority of the currentunlicensed carrier frequency, if the serving cell fulfills a conditionof Srxlev >S_(nonIntraSearchSINR_av), the UE may choose not to performmeasurements on the licensed inter-RAT frequency.S_(nonIntraSearchSINR_av) may be the threshold (in dB) for the licensedinter-RAT frequency measurement, for example, in terms of average SINR.If the multi-beam operation on the unlicensed spectrum(s) is used,S_(nonIntraSearchSINR_av) may be configured. In some of the presentimplementations, if the conditions mentioned above are not fulfilled,the UE may perform measurements of the licensed inter-RAT frequencies.

In some of the present implementations, if the highest-ranked cell (orthe best cell or the strongest cell) on an unlicensed carrier frequency(e.g., the highest-ranked cell is an unlicensed intra-frequency cell oran unlicensed inter-frequency cell) is not suitable to camp on becausethe highest-ranked cell is a part of the “list of 5G System (5GS)forbidden Tracking Areas (TAs) for roaming”, or belongs to a PLMN whichis not indicated as being equivalent to the registered PLMN, thehighest-ranked cell is barred, the UE may consider the highest-rankedcell as a non-suitable cell to camp on for a maximum time period of T(e.g., 300) seconds. In this case, the UE may consider other cells ascandidate cells on the same unlicensed carrier frequency for the cellreselection procedure.

Cells on the unlicensed carrier frequency may be ranked based on theircorresponding measured metric values or other absolute priorityreselection rules. For example, the highest-ranked cell may be the cellhaving the best received radio signal quality among cells on the samecarrier frequency. It should be noted that the “highest-ranked cell,”the “best cell,” and the “strongest cell,” may be interchangeable termsin some of the present implementations.

In some of the present implementations, the T value for the licensedintra-frequency cell case or for the licensed inter-frequency cell casemay be independent of the T value for the unlicensed intra-frequencycell case or for the unlicensed inter-frequency cell case. The T valuesmay be independently configured or predefined for different cases, andthe T values may be different. In some of the present implementations,the T value for the licensed intra-frequency cell case or for thelicensed inter-frequency cell case may be the same as the T value forthe unlicensed intra-frequency cell case or for the unlicensedinter-frequency cell case. In some of such implementations, the T valuesfor different cases may be configured or predefined together.

In some of the present implementations, if the highest-ranked cell on anunlicensed carrier frequency is a non-suitable cell to camp on (e.g.,the UE determines that the highest-ranked cell is not suitable forcamping on), the UE may not consider cells on the same unlicensedcarrier frequency as candidate suitable cells for reselection for amaximum time period of T (e.g., 300) seconds, if at least one cell onother frequencies is ranked by the UE and has a rank value higher than arank threshold. The rank threshold may be preconfigured, broadcast bythe serving cell (e.g., in the SIB2, the SIB3, the SIB4 or the SIB5), orsent via the RRC dedicated signaling (e.g., in an RRC (Connection)Release message, in an RRC Release message with suspend configuration,in an RRC Release message without suspend configuration).

In some of the present implementations, if the highest-ranked cell on anunlicensed carrier frequency is not suitable for camping on, the UE mayconsider cells on the same unlicensed carrier frequency as non-suitablecells for a maximum time period of T seconds if at least one cell onother frequencies fulfills the cell selection criterion S.

In some of the present implementations, if the highest-ranked cell on anunlicensed carrier frequency is determined as a non-suitable cell, theUE may further consider cells on the same unlicensed carrier frequencyas non-suitable cells for a maximum time period of T (e.g., 300) secondsif the measured metric value (e.g., the RSRP value, the RSRQ value orthe SINR value) of at least one cell on other frequencies is above athreshold. The threshold may be preconfigured, broadcast by the servingcell (e.g., in the SIB2, the SIB3, the SIB4, the SIB5), or sent via theRRC dedicated signaling (e.g., in an RRC (Connection) Release message,in an RRC Release message with suspend configuration, in an RRC Releasemessage without suspend configuration).

In some of the present implementations, the UE may be redirected, underthe licensed RAT (e.g., NR)'s control, to an unlicensed carrierfrequency (e.g., to utilize the unlicensed RAT such as the NR-U). If theUE is redirected, under the licensed RAT's control, to the unlicensedcarrier frequency for which a timer T is running, any limitation on thatunlicensed carrier frequency may be removed. The limitation may includeany restriction from allowing the UE to perform cell (re)selectionprocedures on that unlicensed carrier frequency. For example, the UE mayremove the limitation on that unlicensed carrier frequency by stoppingthe timer T. Thus, the UE may perform measurements on that unlicensedcarrier frequency.

In some of the present implementations, the UE may be redirected, underthe unlicensed RAT (e.g., NR-U)'s control, to a licensed carrierfrequency (e.g., NR). If the UE is redirected under unlicensed RAT(e.g., NR-U) control to a licensed carrier frequency for which the timerT is running, any limitation on that licensed carrier frequency may beremoved. The limitation may include any restriction from allowing the UEto perform cell (re)selection procedures on that licensed carrierfrequency. For example, the UE may remove the limitation on thatlicensed carrier frequency by stopping the timer T. Thus, the UE mayperform measurements on that licensed carrier frequency.

In some of the present implementations, if an indication (e.g.,thresServingLowSINR) is broadcast in the system information and morethan Tr (e.g., 1) second has elapsed since the UE began camping on thecurrent serving cell, the UE may perform a cell reselection procedure toselect a cell (e.g., a new suitable cell to camp on) on a higherpriority frequency than the serving frequency. The cell of a higherpriority RAT, a licensed carrier frequency or an unlicensed carrierfrequency may fulfill that the SINR value of the cell is above athreshold (e.g., Thresh_(X, HighSINR)) during a time interval (e.g.,Treselection_(RAT)). Otherwise, the cell reselection to the cell on thehigher priority frequency (e.g., an intra-frequency or aninter-frequency) than the serving frequency may be performed if the cellfulfills Srxlev>Thresh_(X, HighP) during a time interval (e.g.,Treselection_(RAT)) and more than 1 second has elapsed since the UEbegan camping on the current serving cell.

In some of the present implementations, the frequency channel of theselected cell (e.g., the new suitable cell during the cell reselectionprocedure), which may correspond to a higher priority RAT, licensedcarrier frequency or unlicensed carrier frequency, may fulfill that theRSSI value of the frequency is above a threshold (e.g.,Thresh_(X, HighRSSI)) during a time interval (e.g., Treselection_(RAT)).Otherwise, the cell reselection to the cell on a higher priorityfrequency (e.g., an intra-frequency or an inter-frequency) than theserving frequency may be performed, if the cell fulfillsSrxlev>Thresh_(X, HighP) during a time interval (e.g.,Treselection_(RAT)) and more than 1 second has elapsed since the UEbegan camping on the current serving cell.

In some of the present implementations, if an indication (e.g.,thresServingLowCO) is broadcast in the system information and more thanTr (e.g., 1) second has elapsed since the UE camped on the currentserving cell, the UE may perform a cell reselection to a cell on ahigher priority frequency than the serving frequency. The frequencychannel of a cell, of a higher priority RAT, licensed carrier frequencyor unlicensed carrier frequency, may fulfill that the channel occupancyratio value of the frequency is above a threshold (e.g.,Thresh_(X, HighCO)) during a time interval (e.g., Treselection_(RAT)).Otherwise, the cell reselection to the cell on the higher priorityfrequency (e.g., an intra-frequency or an inter-frequency) than theserving frequency may be performed if the cell fulfillsSrxlev>Thresh_(X, HighP) during a time interval (e.g.,Treselection_(RAT)) and more than 1 second has elapsed since the UEbegan camping on the current serving cell.

In some of the present implementations, if there is no special indicator(e.g., thresServingLowSINR, thresServingLowRSSI, thresServingLowCO)broadcast in the system information and more than Tr (e.g., 1) secondhas elapsed since the UE began camping on the current serving cell, theUE may perform a cell reselection to a cell on a higher priorityfrequency than the serving frequency. The selected cell (e.g., a newsuitable cell to camp on) may fulfill that a cell selection RX levelvalue based on RSRP (e.g., Srxlev) is above a threshold (e.g.,Thresh_(X, HighP)) during a timer interval (e.g., Treselection_(RAT)).

In some of the present implementations, the mechanisms mentioned abovemay be applied to a cell reselection procedure to change the originalsuitable cell of the UE from a cell in the licensed carrier frequency toa cell in the unlicensed carrier frequency, or from a cell in theunlicensed carrier frequency to a cell in the licensed carrierfrequency, or from a cell in the unlicensed carrier frequency to a cellin the unlicensed carrier frequency, or from a cell in the licensedcarrier frequency to a cell in the licensed carrier frequency.

In some of the present implementations, if a UE camping on a cell in asource frequency reselects to a cell in a target frequency, the UE maystart a timer based on a timer value. Before the timer expires, the UEmay not measure and/or reselect a cell in the source frequency. The UEmay be configured with the timer value via the system information (e.g.,the SIB1, other SI (e.g., the SIB2 or the SIB3)) or the dedicatedsignaling (e.g., the RRC (Connection) Release message, the suspendconfiguration in the RRC Release message, the RRC Release message withsuspend configuration, the RRC Release message without suspendconfiguration) by the cell on the source frequency. In some of thepresent implementations, the timer value may be preconfigured orpredefined. In some of the present implementations, the UE may stop thetimer if the UE cannot reselect any cell in another frequency. In otherwords, the UE may deprioritize the source frequency to the lowestpriority among all available frequencies (e.g., when the timer isrunning). In some of the present implementations, if the UE camping on atarget cell reselects to another target cell in the third frequency, theUE may stop the timer for the source frequency. Moreover, the UE maystart the timer for the target frequency.

In some of the present implementations, the UE may rank all cells on theunlicensed intra-frequency or unlicensed inter-frequency that fulfillthe cell selection criterion S. The UE may rank cells based on thecell-ranking criterion R_(s) for the serving cell and R_(n) forneighboring cells. In some of the present implementations, thecell-ranking criterion R_(s) for the unlicensed serving cell and thecell-ranking criterion R_(n) for the unlicensed neighboring cells (e.g.,in the unlicensed intra-frequency or in the equal priority unlicensedinter-frequency) may be defined by R_(s)=Q_(meas, s)+Q_(rmd, s) andR_(n)=Q_(meas, n)+Q_(rmd, n), where Q_(meas, s) may be the measuredmetric value (e.g., the RSRP value, the RSRQ value, or the SINR value)used in the cell reselection procedure, Q_(rmd, s) may be the adjusteditem (e.g., a hysteresis value), Q_(meas, n) may be the measured metricvalue used in the cell reselection procedure, and Q_(rmd, n) may be theadjusted item (e.g., offset values depending on the unlicensedintra-frequency or inter-frequency). The comparison between R_(s) andR_(n) may be based on the same measured metric. In some of the presentimplementations, the UE may receive the values of Q_(rmd, s) andQ_(rmd, n) via the system information (e.g., the SIB2, the SIB3, theSIB4, the SIB5 or others) or via the dedicated signaling (e.g., an RRC(Connection) Release message, RRC

Release message with suspend configuration, RRC Release message withoutsuspend configuration) from the serving cell.

In some of the present implementations, the UE may rank the (unlicensed)cells according to the R criteria and calculate the R values (e.g.,R_(s) and R_(n)) using the averaged measured metric results (e.g., theaveraged RSRP/RSRQ/SINR values) of the corresponding cells.

In some of the present implementations, the UE may re-rank the cellsbased on the UE's registered PLMN or equivalent PLMN. The re-ranked cellranking list may include all cells belonging to the same PLMN. Forexample, the UE may re-rank the cells by removing the cells notbelonging to the registered PLMN or equivalent PLMN from the originalcell ranking list. In this case, the original cell ranking list mayinclude cells belonging to different PLMNs.

In some of the present implementations, the UE may base on thesignal-strength-related measurement quantity (e.g., RSRP, RSRQ, SINR) torank the cells. The cells belonging to different PLMNs on the samecarrier frequency may be ranked together, which we may refer to“original cell ranking list”. If the re-rank rule is applied, there-ranked cell ranking list may include all cells belonging to the UE'sregistered PLMN or equivalent PLMN. In some of the presentimplementations, the UE may perform the cell reselection procedure basedon the original cell ranking list. In some of the presentimplementations, the UE may perform the cell reselection procedure basedon the re-ranked cell ranking list. In some of the presentimplementations, the UE may use the re-ranked cell ranking list toperform an intra-frequency cell reselection procedure and/or aninter-frequency cell reselection procedure. For example, the UE may(re)select the highest-ranked cell among cells listed in the re-rankedcell ranking list on the licensed spectrum(s). For another example, theUE may reselect the highest-ranked cell among cells listed in there-ranked cell ranking lists on the unlicensed spectrum(s). For example,the UE may (re)select the highest-ranked cell among cells listed in there-ranked cell ranking list including cells on the licensed spectrum(s)and unlicensed spectrum(s) and belonging to the same PLMN. In some ofthe present implementations, the cell ranking list on the licensedspectrum(s) may be regarded as a re-rank cell ranking list if the cellranking list on the licensed spectrum(s) includes cells belonging to thesame PLMN.

In some of the present implementations, if the UE has at least twooriginal cell ranking lists wherein each list is corresponding to oneunlicensed carrier frequency, the UE may select a cell that satisfiesthe following two conditions as a suitable cell: (1) the cell belongs tothe selected/registered/equivalent PLMN, and (2) the cell is thehighest-ranked cell among cells listed in the at least two original cellranking lists. Furthermore, the selected cell may not be barred.

In some of the present implementations, if the indication (e.g.,rangeToBestCell) is not configured, the UE may perform the cellreselection procedure to select a new suitable cell ranked as the bestcell. The best cell may be listed in the original cell ranking list orthe re-ranked cell ranking list. In some of the present implementations,if the best cell (or the highest-ranked cell) is found to benon-suitable (e.g., not belonging to the UE's registered PLMN orequivalent PLMN, not fulfilling cell selection criterion S), the UE mayselect the next best cell (or the next highest-ranked cell) as the newsuitable cell. The ranking of the next best cell (or the nexthighest-ranked cell) is lower than that of the best cell (or thehighest-ranked cell).

In some of the present implementations, if the UE finds a selected cellto be non-suitable (e.g., not belonging to the UE's registered PLMN orequivalent PLMN), the UE may select the next cell whose ranking is thenext lower to the previously selected non-suitable cell. In some of thepresent implementations, if the best cell is found to be non-suitable(e.g., not belonging to the UE's registered PLMN or equivalent PLMN, notfulfilling cell selection criterion S), the UE may remove the cellsbelonging to the same PLMN as the best cell in the original cell rankinglist.

In some of the present implementations, if the indication (e.g.,rangeToBestCell) is configured, the UE may perform a cell reselectionprocedure to select a new suitable cell. The new suitable cell may havethe highest number of beams above a threshold (e.g., an SINR-valuedthreshold, an RSRP-valued threshold, or an RSRQ-valued threshold) amongthe cells whose R value is within the indication (e.g., rangeToBestCell)of the R value of the cell ranked as the best cell. For example, if theUE calculates the R value of a cell based on an (averaged) SINR value,the UE may count the number of beams above an SINR-valued threshold ofthe cell. In some of the present implementations, if there are multiplesuch cells, the UE may perform the cell reselection procedure to selectthe highest-ranked cell among them.

In some of the present implementations, if the indication (e.g.,rangeToBestCell) is configured, the UE may perform a cell reselectionprocedure to select a new suitable cell belonging to the UE's registeredPLMN (or equivalent PLMN) and having the highest number of beams above athreshold (e.g., an SINR-valued threshold, an RSRP-valued threshold, oran RSRQ-valued threshold) among the cells whose R value is within theindication (e.g., rangeToBestCell) of the R value of the cell ranked asthe best cell. In some of the present implementations, the best cell maybe listed in a re-ranked cell list. In some of the presentimplementations, the best cell may or may not belong to the UE'sregistered PLMN (or equivalent PLMN). For example, if the UE calculatesthe R value of a cell based on an (averaged) SINR value, the UE maycount the number of beams above an SINR-valued threshold of the cell. Insome of the present implementations, if there are multiple such cells,the UE may perform the cell reselection procedure to select thehighest-ranked cell among them.

In some of the present implementations, the cell may broadcast a channeloccupancy ratio value or an RSSI value based on the cell's measurementon the unlicensed carrier frequency. If the cell's broadcast channeloccupancy ratio value is above a threshold, the UE may not (re)selectsuch a cell as a suitable cell to camp on. Similarly, if the cell'sbroadcast RSSI value is below a threshold, the UE may not (re)selectsuch a cell as a suitable cell. In some of the present implementations,if the cell's broadcast channel occupancy ratio value is above athreshold, the UE may perform an inter-frequency cell reselectionprocedure or an inter-RAT cell reselection procedure to search for a newsuitable cell in other frequencies.

In some of the present implementations, if the cell's broadcast RSSIvalue is below a threshold, the UE may perform an inter-frequency cellreselection procedure or an inter-RAT cell reselection procedure tosearch for a new suitable cell in other frequencies. If the UE receivesthe multiple RSSI values from the cell, the UE may compare the averagevalue of the RSSI values with the threshold. In some of the presentimplementations, the threshold may be broadcast to the UE or sent to theUE via the dedicated signaling. In some of the present implementations,the threshold may be a pre-defined value (e.g., determined based on UEcategories, UE target service types, or other UE characteristics). Insome of the present implementations, the UE may adjust the cell's rankbased on the cell's broadcast channel occupancy ratio value or RSSIvalue.

In some of the present implementations, the mentioned dedicatedsignaling may refer to (but not limited to) RRC message(s). The cell maytransmit the dedicated signaling to the UE, wherein the dedicatedsignaling may be RRC (Connection) Setup message, RRC (Connection)Reconfiguration message, RRC Connection Reconfiguration messageincluding the mobility control information, RRC ConnectionReconfiguration message without the mobility control information inside,RRC Reconfiguration message including the configuration with sync, RRCReconfiguration message without the configuration with sync inside, RRC(Connection) Resume message, RRC (Connection) Reestablishment message,RRC (Connection) Reject message, RRC

(Connection) Release message, RRC Release message including suspendconfiguration, RRC Release message without suspend configuration insideand UE Capability Enquiry message, etc. The UE may transmit thededicated signaling to the cell, wherein the dedicated signaling may beRRC (Connection) Setup Request message, RRC (Connection) Setup Completemessage, RRC (Connection) Reconfiguration Complete message, RRC(Connection) Resume Request message, RRC (Connection) Resume Completemessage, RRC (Connection) Reestablishment Request message, RRC(Connection) Reestablishment Complete message, RRC System InformationRequest message, UE Assistance Information message, and UE CapabilityInformation message, etc.

The RRC_IDLE/RRC_INACTIVE UE may camp on a cell, which may refer to a“camped cell”. The RRC_CONNECTED UE may be served by a serving cell. Theserving cell may be a camped cell to the UE when the UE enters inRRC_IDLE/RRC_INACTIVE. The camped cell may be a serving cell to the UEwhen the UE enters in RRC_CONNECTED. If the UE can measure the radiosignal strength from a cell, such cell may be a detected cell to the UE.

FIG. 8 is a block diagram illustrating a node for wirelesscommunication, in accordance with various aspects of the presentdisclosure. As shown in FIG. 8, a node 800 may include a transceiver820, a processor 828, a memory 834, one or more presentation components838, and at least one antenna 836. The node 800 may also include an RFspectrum band module, a BS communications module, a networkcommunications module, and a system communications management module,Input/Output (I/O) ports, I/O components, and power supply (notexplicitly shown in FIG. 8). Each of these components may be incommunication with each other, directly or indirectly, over one or morebuses 840. In one implementation, the node 800 may be a UE, a BS, or anyother apparatus of wireless communications that performs variousfunctions described herein, for example, with reference to FIGS. 1through 7.

The transceiver 820 having a transmitter 822 (e.g.,transmitting/transmission circuitry) and a receiver 824 (e.g.,receiving/reception circuitry) may be configured to transmit and/orreceive time and/or frequency resource partitioning information. In someof the present implementations, the transceiver 820 may be configured totransmit in different types of subframes and slots including, but notlimited to, usable, non-usable and flexibly usable subframes and slotformats. The transceiver 820 may be configured to receive data andcontrol channels.

The node 800 may include a variety of computer-readable media.Computer-readable media may be any available media that may be accessedby the node 800 and include both volatile (and non-volatile) media, andremovable (and non-removable) media. By way of example, and notlimitation, computer-readable media may comprise computer storage mediaand communication media. Computer storage media may include bothvolatile (and/or non-volatile), as well as removable (and/ornon-removable) media implemented in any method or technology for storageof information such as computer-readable instructions, data structures,program modules or data.

Computer storage media may include RAM, ROM, EEPROM, flash memory orother memory technology, CD-ROM, Digital Versatile Disks (DVD) or otheroptical disk storage, magnetic cassettes, magnetic tape, magnetic diskstorage or other magnetic storage devices. Computer storage media do notcomprise a propagated data signal. Communication media may typicallyembody computer-readable instructions, data structures, program modulesor other data in a modulated data signal such as a carrier wave or othertransport mechanism and includes any information delivery media. Theterm “modulated data signal” may mean a signal that has one or more ofits characteristics set or changed in such a manner as to encodeinformation in the signal. By way of example, and not limitation,communication media may include wired media such as a wired network ordirect-wired connection, and wireless media such as acoustic, RF,infrared and other wireless media. Combinations of any of the aboveshould also be included within the scope of computer-readable media.

The memory 834 may include computer-storage media in the form ofvolatile and/or non-volatile memory. The memory 834 may be removable,non-removable, or a combination thereof. Example memory includessolid-state memory, hard drives, optical-disc drives, etc. Asillustrated in FIG. 8, the memory 834 may store computer-readable andcomputer-executable instructions 832 (e.g., software codes) that areconfigured to, when executed, cause the processor 828 to perform variousfunctions described herein, for example, with reference to FIGS. 1through 7. Alternatively, the instructions 832 may not be directlyexecutable by the processor 828 but be configured to cause the node 800(e.g., when compiled and executed) to perform various functionsdescribed herein.

The processor 828 (e.g., having processing circuitry) may include anintelligent hardware device, e.g., a Central Processing Unit (CPU), amicrocontroller, an ASIC, etc. The processor 828 may include memory. Theprocessor 828 may process the data 830 and the instructions 832 receivedfrom the memory 834, and information through the transceiver 820, thebaseband communications module, and/or the network communicationsmodule. The processor 828 may also process information to be sent to thetransceiver 820 for transmission through the antenna 836, to the networkcommunications module for transmission to a core network.

One or more presentation components 838 may present data indications toa person or other device. Examples of presentation components 838 mayinclude a display device, speaker, printing component, vibratingcomponent, etc.

From the above description, it is manifested that various techniques maybe used for implementing the concepts described in the presentapplication without departing from the scope of those concepts.Moreover, while the concepts have been described with specific referenceto certain implementations, a person of ordinary skill in the art mayrecognize that changes may be made in form and detail without departingfrom the scope of those concepts. As such, the described implementationsare to be considered in all respects as illustrative and notrestrictive. It should also be understood that the present applicationis not limited to the particular implementations described above, butmany rearrangements, modifications, and substitutions are possiblewithout departing from the scope of the present disclosure.

What is claimed is:
 1. A User Equipment (UE) for wirelesscommunications, the UE comprising: one or more non-transitorycomputer-readable media having computer-executable instructions embodiedthereon; and at least one processor coupled to the one or morenon-transitory computer-readable media, and configured to execute thecomputer-executable instructions to: read system information of aplurality of cells on a first carrier frequency to obtain identificationinformation of a plurality of Public Land Mobile Networks (PLMNs);report, by an Access Stratum (AS) entity of the UE, the identificationinformation of the plurality of PLMNs to a Non-Access Stratum (NAS)entity of the UE; select, by the NAS of the UE, one of the plurality ofPLMNs as a selected PLMN; search for the plurality of cells on the firstcarrier frequency during a cell selection procedure; and select asuitable cell belonging to the selected PLMN from the plurality of cellson the first carrier frequency based on the cell selection procedure. 2.The UE of claim 1, wherein the at least one processor is furtherconfigured to execute the computer-executable instructions to: perform acell reselection procedure to select a new suitable cell, wherein thenew suitable cell is a non-highest-ranked cell among all cells on thefirst carrier frequency and belongs to one of the selected PLMN and anequivalent PLMN that is indicated as being equivalent to a registeredPLMN of the UE.
 3. The UE of claim 2, wherein the non-highest-rankedcell and a highest-ranked cell on the first carrier frequency belong totwo PLMNs of the plurality of PLMNs.
 4. The UE of claim 1, wherein theat least one processor is further configured to execute thecomputer-executable instructions to: perform a cell reselectionprocedure to select a new suitable cell, the cell reselection procedurecomprising: determining whether the new suitable cell is on a secondcarrier frequency after determining that a total number of non-suitablecells on the first carrier frequency reaches a specific number.
 5. TheUE of claim 4, wherein the cell reselection procedure further comprises:selecting, from one or more cells on the second carrier frequency, ahighest-ranked cell as the new suitable cell when the highest-rankedcell belongs to one of the selected PLMN and an equivalent PLMN that isindicated as being equivalent to a registered PLMN of the UE;determining that the highest-ranked cell is a non-suitable cell when thehighest-ranked cell does not belong to one of the selected PLMN and theequivalent PLMN; and prohibiting the non-suitable cell from beingselected as the new suitable cell for a period of time.
 6. The UE ofclaim 5, wherein the cell reselection procedure further comprises:determining the highest-ranked cell by ranking the one or more cells onthe second carrier frequency based on a received radio signal quality.7. The UE of claim 4, wherein the at least one processor is furtherconfigured to execute the computer-executable instructions to:deprioritize the first carrier frequency for cell reselection for aperiod of time after determining that the total number of non-suitablecells on the first carrier frequency reaches the specific number.
 8. TheUE of claim 1, wherein the system information includes PLMN-typeinformation indicating at least one PLMN type associated with theplurality of cells.
 9. The UE of claim 1, wherein the at least oneprocessor is further configured to execute the computer-executableinstructions to: provide a message by the NAS entity of the UE to the ASentity of the UE, the message indicating which of one or more PLMN typesare supported by the UE, wherein the one or more PLMN types include apublic PLMN type, a private PLMN type, and a public and private PLMNtype.
 10. The UE of claim 1, wherein the first carrier frequency is anunlicensed carrier frequency.
 11. A method performed by a User Equipment(UE) for wireless communications, the method comprising: reading systeminformation of a plurality of cells on a first carrier frequency toobtain identification information of a plurality of Public Land MobileNetworks (PLMNs); reporting, by an Access Stratum (AS) entity of the UE,the identification information of the plurality of PLMNs to a Non-AccessStratum (NAS) entity of the UE; selecting, by the NAS of the UE, one ofthe plurality of PLMNs as a selected PLMN; searching for the pluralityof cells on the first carrier frequency during a cell selectionprocedure; and selecting a suitable cell belonging to the selected PLMNfrom the plurality of cells on the first carrier frequency based on thecell selection procedure.
 12. The method of claim 11, furthercomprising: performing a cell reselection procedure to select a newsuitable cell, wherein the new suitable cell is a non-highest-rankedcell among all cells on the first carrier frequency and belongs to oneof the selected PLMN and an equivalent PLMN that is indicated as beingequivalent to a registered PLMN of the UE.
 13. The method of claim 12,wherein the non-highest-ranked cell and a highest-ranked cell on thefirst carrier frequency belong to two PLMNs of the plurality of PLMNs.14. The method of claim 11, further comprising: performing a cellreselection procedure to select a new suitable cell, the cellreselection procedure comprising: determining whether the new suitablecell is on a second carrier frequency after determining that a totalnumber of non-suitable cells on the first carrier frequency reaches aspecific number.
 15. The method of claim 14, wherein the cellreselection procedure further comprises: selecting, from one or morecells on the second carrier frequency, a highest-ranked cell as the newsuitable cell when the highest-ranked cell belongs to one of theselected PLMN and an equivalent PLMN that is indicated as beingequivalent to a registered PLMN of the UE; determining that thehighest-ranked cell is a non-suitable cell when the highest-ranked celldoes not belong to one of the selected PLMN and the equivalent PLMN; andprohibiting the non-suitable cell from being selected as the newsuitable cell for a period of time.
 16. The method of claim 15, whereinthe cell reselection procedure further comprises: determining thehighest-ranked cell by ranking the one or more cells on the secondcarrier frequency based on a received radio signal quality.
 17. Themethod of claim 14, further comprising: deprioritizing the first carrierfrequency for cell reselection for a period of time after determiningthat the total number of non-suitable cells on the first carrierfrequency reaches the specific number.
 18. The method of claim 11,wherein the system information includes PLMN-type information indicatingat least one PLMN type associated with the plurality of cells.
 19. Themethod of claim 11, further comprising: providing a message by the NASentity of the UE to the AS entity of the UE, the message indicatingwhich of one or more PLMN types are supported by the UE, wherein the oneor more PLMN types include a public PLMN type, a private PLMN type, anda public and private PLMN type.
 20. The method of claim 11, wherein thefirst carrier frequency is an unlicensed carrier frequency.